Confidence is something important if you want to be seen as anything other than a hobbyist in anything. Confidence is what breaks the barrier between being really good and getting the attention for it, and being really good and constantly feeling bad no matter how far you go.
To start, every artist starts somewhere. Doesn't matter what field of art it is, music, literature or the more physical forms. Some have a leg up because they see something others don't see quite as easily. Doesn't change that fact. I've seen mediocre artists rise up and completely blow away the 'naturally talented' ones. On that note, I can say that confidence can sometimes simply become OVERconfidence and cause some major ego tripping that pisses everyone off. It's the opposite side of the coin of irritation that is interacting with artists. If you want a little perspective, I had a teacher in grade school tell me that I should probably look into something other than drawing when I was in second grade. I'm far from what I'd consider the best, but damn if that path behind isn't treacherous and long.
Anyway, here's a few points for those that lack confidence to start working on so they can stop being so lame about it and possibly pissing everyone around them off.
For starters, take the compliment! Someone says it looks good, then it does to them. Doesn't matter what you see, you don't have to say it! They see something they like, THAT YOU MADE, let them say so. Don't say, "I'm glad you like it, but XXXXX part of it kinda sucks." I do some minor critiquing in my own comment box and try to leave it at that if there's something I don't like. Even that crosses the line on this point sometimes. Every artist of every kind ever is guilty of this at some point in time. Get over it! Suck it up! <add another cliched reverse point of you being lame here>
If you feel like complimenting another artist, do so. Do NOT make the comment about yourself though in terms of how much you suck or will never be as good. You are at your own level with your own level of understanding. There might be something you get that they don't. They might see your stuff and see that. Part of my training was a pretty in depth head slamming on 'how to critique'. It's infuriating to see someone critiquing another and use words like suck, or not good in relation to themselves. DON'T SUCK UP OR PUT YOURSELF DOWN WHEN DEALING WITH SOMEONE ELSE'S WORK!!! You are there to look at their stuff, not compare to how bad you might be. If you go to compare make it a comparative analysis, not a whine-fest. If you want to know how it's done, don't be afraid to ask. If they say that they can't say, they might be busy or simply not know exactly how they do it in a way they can explain, get over it.
Also, whether artist or fan, please comment on things. Not enough people comment on art out there and it's part of what can lead to insecurities in many budding artists in every field. Hell, it can make even a seasoned pro feel like something is wrong and obsess about something.
Try to be positive about your own work. If you put time and real effort into it, be proud of that. If someone comes in pointing things out that might be off, take it as what it is, a chance to grow. Not all critiques, real critiques, are full of sugar, unicorns and butterflies. Some are downright cruel. Sometimes that's because the one delivering the message is an ass, but but sometimes it's because it's true. Both points can happen, but it's the truth of it that matters, not how they said it or how much of a douche the messenger is. Be proud of what you did and see everything you do, no matter how good or bad, as a stepping stone. Everything you create is a chance to grow, be proud you took that step. Even if you slip or falter, you still took that step. Be positive about it, damn it.
By that same token, don't get down if no one's looking. That's just how it is. Keep in mind how big the internet, or even just the site you are posting to might be. People tend to go where they know. Sometimes they trailblaze, but even when they do they don't always stray too far. Being noticed can take time and interest in stuff can wane periodically. Everyone is insecure about their stuff, but the cool kids try to keep it contained. Keeping it down will likely get more people talking to you. This means they are more likely to talk ABOUT you. That's how those kids get cool. If you talk about how lame you are, people see it as a fact that you might just disappear into the hinterlands and don't feel like getting attached.
If you feel like you are being overshadowed, deal with it. It's part of the industry/fandom/internet/world. Jealousy is ugly. I feel it all the damn time, but just choke it down. Other creators of anything feel it too. I see it on their faces in flash moments among even the best of the best in all industries when someone tops them. Keeping a lid on it lets you focus on getting out of that shadow. You are one person, they are another. Even if you choose to walk the same path, your feet will fall differently. The path is different for everyone and if you work long enough, hard enough, you will be casting your own shadow as the light on you moves while you climb that trail. If you see someone else as better, try to find out how they are. Sometimes those great creators are willing to glean a bit of information that can push you along and make you feel a little less in the shade.
You will be making crappy art. It's inevitable. Even the greatest of the great have off days/weeks/months. It's called a funk when someone backslides, it's called inexperience when someone hasn't learned yet. If you don't know how to do something, you don't know. Doesn't mean you outright suck, it just means you need to move on and get to knowing it. If you can't seem to get a line/word straight enough, put it down there anyway. Even if a part of something seems to ruin it, you are still the one that made it. You, not someone else, are the creator. Make things. Make them as often as you can. If you feel like it, make and remake the same thing until you do manage to get that one point of it to shine. Polish your work by either pumping it out item by item, or working on getting that one piece to shine. Know when to move on though. You could spend forever working on the same thing and never grow past it if you aren't careful. Don't whine about how much something sucks, do something about it or move on. Grow...
One thing to keep in mind above all others in helping you be confident. You are creating. This means you are already there in some respects. You are surviving the thinning of the herd the longer you hold on. People drop out of the game every minute of every day. The fact you are still hanging on already means you are winning. Now, don't get arrogant about it and focus on growing. Even if you make it you can still be better.
Don't stop creating. I have a three part mantra, credo, support point, belief set, whatever you want to call it that I came up with many years ago that's kept me and several other people I've explained it to moving that help keep one focused and somewhere better between insecurity and overconfidence. It's right in my profile and has been since day one around here. Create, balance, believe. Never stop creating. Believe in what you create. Strike a balance between those points because to create without belief in the creation is to create without substance or potential for growth and to believe too much in your creation can make you turn stagnant and stop growing. It's hovering between those thoughts that confidence and true growth lie. Keep it in mind and never... stop... growing... See the beauty in what you create, no matter how awful it might be to your eyes.
BE CONFIDENT DAMN IT!!!