leaving my boyfriend

(cross posting with teen and adult relationships because i turned 18 a while ago and it’s a weird inbetween point)

i’ve been dating my current boyfriend for almost 10 months now. got together a month after my longest relationship ended. it’s been roughly a year.

my ex boyfriend came back and essentially still loves me which made me realize i didn’t have that self reflective stage where i recognized my own faults before jumping back into a relationship.

i also realized some negative traits of my current boyfriend and was partially projecting feelings from my ex onto him.

how do i say that without breaking him?