Social media is awash with it at the moment. People talking about their new year resolutions, detox plans, and how things are going to be different this year. The desire to be a better person isn't in itself a bad thing, it is what may lie underneath that desire that can be toxic. Our desire for self-improvement can come from two motivations. The first is to learn, have new experiences, develop healthier relationships with other people, and generally feel more content with ourselves. No problems there. However, I think if we scrape below the surface of many people's desire for self-improvement, the motivation is actually self-loathing: a hatred of ourselves for not being perfect. This is toxic because nobody can be perfect, so no amount of self-improvement is ever going to take this self-loathing away. When the self-improvement 'fails', the self-loathing turns into low self-esteem, which can cause anxiety and depression.
So, for the sake of your mental health, rather than making a new years resolution is improve yourself, why not make a new years resolution is be ok with yourself - just as you are, imperfect.
If only it were that simple. The problem is, being ok with imperfection isn't something we are encouraged to be - our parents, teachers, bosses, and the entire advertising industry spend most of their time encouraging us to be better. The motivation for this is often well intentioned (although in the case of advertising, the motivation is to make us buy stuff that we think will make us feel or be better). However well intentioned, the unintended consequence of constantly being encouraged to improve ourselves, is that we can assume that we are never ever good enough as we are, and we believe that any imperfection makes us unlikable, unsuccessful, and unlovable. We end up not liking ourselves very much.
So, if you are going to make any new years resolutions, I would suggest making a few tweaks to the way you make them. First, make one of the resolutions that you are going to try and accept and like yourself as you are - warts and all. Then, any other resolutions can start with "it would be nice if...", rather than "i must...". Then, if the resolution fails (and evidence shows that it probably will), you will be ok with it, because you are ok with imperfect you.