Dissatisfaction, Blame, and Criticism are the three main ingredients to eternal unhappiness.
Accept people for who they are, because as soon you mold them to be “just right”, they will at that point have a become “carbon copy” of you. That’s not such a bad idea, if your plan is to make clone copies of yourself, so that you always have a “like minded” person to talk to wherever in the World you travel to. But it’s not such a great idea in a “Romantic relationship”, where we’re “unwittingly” attracted to qualities and traits, that are “completely opposite” to our own. When you kill the very traits that made the other person “sexy” and “appealing” you will have pretty much “punctured” the “romance” out of the relationship. After that, even if the relationship does “survive”, it would be based solely on “non-romantic” love (i.e. the kind that exists among family members and cult members).
Trying to “fix” people is pretty much the equivalent of performing heart surgery on someone we care about without any knowledge about heart surgery or surgery. And without even knowing where the heart is in the first place.
Besides, would you wanna be around someone who’s always trying to change you? Or someone who only sees you for your “shortcomings”?