i still find each day too short for all the thoughts I want to think, all the walks I want to take, all the books I want to read, and all the friends I want to see. - John Burroughs (I'll add, and all the sleep I want to sleep :)
I picked this quote because I believe that Finny felt like this when he returned to Devon. When he found out Gene was going to leave him to go to war, Finny felt hurt. He felt he wasn't as important to Gene as he thought he was.
The process of letting go is so especially painful process but you need to let go, Otherwise we just keep ourselves stuck in the same place. It's not healthy to fantasize about a future with this person.