There were large periods of time where Marle was simply alone. Sure, she had Tammy in all her various forms to have as company, but for someone to actually talk to? She had no one. So, she simply learned to grow accustomed to the silence and the tranquility of nature and it was easy for her to enjoy a lazy afternoon and literally do nothing. A butterfly landing on her hoof could entertain her for hours as she watched it. With Marle, she could easily go to a zen place and get lost within her mind - which later suited Max fine at times when he wasn't feeling very social himself. They could both be together in the same room, separately.