Next time you don't manage to follow through to do sth you tried to do on a consistent basis, i.e. meditation every day, working out, eating healthy, idk, instead of judging, doubting and feeling bad about yourself think of the fact that this is apparently something you deeply care about it.
That is a great learning and you should take it to prioritise it more over time. You already did your first steps. Give yourself the pleasure of feeling great after doing it and knowing you put a lot of value on self-care and self-esteem.
On the other side, if you basically just feel bad because you see yourself as a person who needs to push through even though you actually don't like the activity. Well, then it's maybe not for you and that's ok. But don't use that as a simple excuse for treating your body and mind poorly.
Might as well be that the current setup is not working, i.e. if you want to floss, might as well be enough to do it in the morning hours when you are still full of willpower, instead of being exhausted at night and talking yourself out of it.