Every single person in this world has a bunch of physical, but mostly psychological, negative traits which can be deemed toxic in excess, such as the tendency to nag, complain, self hate, under or over confidence, jealous, anxious, vain, or ill tempered generally. Accepting these traits is the first step to fixing and embracing them. These traits cane only be changed and controlled to an extent, so after that, you will just have to accept yourself as you are and admit that you have these traits and may be forced to exercise them from time to time, either willingly or unwillingly.
It is very difficult to recognise these traits within yourself so we often rely on other people to tell us. This can have two problems. Number one, we may not be willing to listen and get offended. This depends on both our mood and personality and the other person’s way of telling us. And second, our friends and family may be too hesitant or unwilling to tell us honestly. Then we are on our own. These traits can escape us if we live alone or are generally very busy. So, if a partner takes up the tough job of holding up a mirror, does not mean that we are difficult to love.
The partner simply has the unfortunate job of being the bearer of bad news. They were aware of these traits for a while and yet still loved you and eventually decided to inform you as you are the only one with the decision power and ability to do something about your traits. Instead of denying them, accept them as you are not the only person in the world with some negative traits. Also, don’t engage in a battle of faults with your partners by vindictively pointing out their flaws. They may simply be doing you a favor.