I also dislike that but I think in this story it was alright to do it because they needed time for themselves alone in order to work on themselves. Still would've prefered it without though.
You totally are right protagonist has serious psychological problems so he needs time to deal with his problems but writers use this technic so much whether it is necessary or not LOL so I sick of it ┗( T﹏T )┛
I just don't get why they have to come back together after five or ten years in mangas. It really is necessity for the plot ┑( ̄Д  ̄)┍