Is this really an INTP specific question? I'm sure everyone's gone through that at some point.
Anyway, I guess I kind of missed out on childhood a bit. I grew out of playground games before my other friends, and I always wanted to be older so I could do more. I started writing stories at a really young age and I was really hard on myself about not being good and the fact that I had never finished anything decent. I think pretty far ahead of myself, so I do miss out on being a teenager too. I try to look at it positively. A lot of people my age waste their time trying to fit in and look cool, doing things - or people - that could completely ruin their future. Maybe I'll be more prepared for adult life.
That, or I'll spend my young adult years hating myself because I'm not some high-flying, high-powered, high-earning CEO of a worldwide company.
If I get there, I'll hate myself because it's not universe-wide.