A book/novel about someone that finds his previous self?

I am not looking for a book about finding my “true self”. I am looking for a book about someone on a journey that puts him in contact with his previous self or something about him/her that was lost along the way.

A little context: I don´t remember me being too hard on myself as i am now and i think i used to be more relaxed about enjoying the little things (like when i was a kid or when i was a teenager). Nowadays it all just feels like work and obligations.

by ImperaOne