<human>: Can you condense the text into a few key points?

hey r/relationships. i [29f] don't post here often, but really need some advice. i was browsing reddit randomly (i'm admittedly not a regular user) and came across a post that was actually written by my BF [29m]. we live together and have been dating for nearly 3 years. naturally, it's fairly serious by this point, we've talked marriage, future, etc. here is his post:

"There is always the one that got away... the one that still hurts. I'll spare you all the gory details, unless you want them later, but suffice it to say that due to my shortsightedness and immaturity I feel like I lost the one girl that I was meant to be with. It's now been 4 years since I broke up with her and I still think about her pretty much every day."

as i read the post, i felt that feeling… shaking, after being punched in the gut and having all of your energy completely drained. i approached him about his post (of course i was very upset) and he assured me that it was just a 'moment of weakness', just a day where he felt 'self-indulgent' and that he truly cared about me. i wasn't necessarily angry at him, a person can't help how they feel and i respect that. we talked about our relationship and pretty much smoothed things over - he's been very loving otherwise & I like to think we have a pretty healthy relationship. but I can't get over this so easily, especially feeling like i'm constantly being compared to someone else in some other context, and the fact that he clearly feels like maybe i'm not the person he was 'meant to be with'. 

What do you think? Am I hanging onto something that's trivial? Or are we choosing a 'healthy relationship' and mediocrity over something that's real?
<bot>: my [29f] live-in BF [29m] of 3yrs is still stuck on his ex, regretting choices he made 4 years ago, thus challenging the legitimacy of our relationship.