This poem has a lot of good things about it! Rhyme scheme helps not only with rhythm but puts enunciation on the right words - really highlighting the pain this character is feeling. It tells a clear story, of regret, and almost subverts expectations with the heartwarming ending. The progression of rhetorical questions structurally is something I also find interesting. This character progresses from self victimisation to looking outwards - for opportunities to change - before returning back to their anxieties "will I be too bold?" and it's nice to see the non-linear thinking people experience universally when looking back at past, regretful events.
I think, also, building on what's been said about the grammar, some things can be omitted for a more direct effect. But rather than a subtract approach - I think making use of potential caesura's (.) or hyphens (-) here would be amazing
For example:
'll beg, I'll cry-
I'll make them feel I'm sorry.
~~And ~~Tell them how badly I missed them (either - or .)
I love them.
~~The ~~ Our past was immaturity' (Or you could change immaturity to immature, does mess up rhythm though hehs)
I'm not too concerned over grammar related things, because once you know how to use them, you can break them all you want. It's a lovely poem, and the message you're trying to deliver does land, but it's minor changes that make it even stronger!