Honestly, I always find it difficult to process how someone can begrudge somebody else something that makes them feel better and helps them to unwind, especially if it isn't hurting anyone. Diapers and regression are not harmful ways of de-stressing, in fact they are a very wholesome way to de-stress, for me, my diapers and my baby-time are wholly therapeutic, they are much healthier forms of stress relief than drugs or smoking. I can understand a parent not wanting their child to engage while around them, I can even understand the parental viewpoint of "my house, my rules. When you're on your own, you can wear diapers as much as you want", but I can't understand why some of them treat diapers and regression as some morally unconscionable taboo that you should try to suppress or do away with. Make of this what you will, it seems you have a somewhat understanding parent on your hands, so this might not entirely apply.
First off, there is no surefire way to quit or curb ABDL habits and desires, though there is a way to limit and self-regulate them. For instance, if you want to please your mother, but still want to wear, simply wear diapers discretely and in the privacy of your own room when you have the time i.e. after your major responsibilities are taken care of. Wearing discretely is also a good way to avoid being found out or receiving further talks/lectures. You're 21, your mother should respect your privacy enough to allow you some time, space and freedom to indulge on the down-low and without her knowing.
Then again, if she understands or tolerates your DL tendencies and she simply wants you to branch out and find other means of relieving stress, as you have outlined in some of your responses, then I think that is a fair request that you can entertain. I'll even agree with her on this front, it's good to be a diverse and well-rounded individual, as such, it's good to have a few interests that can de-stress you. For instance, diapers and regression are huge forms of stress relief for me, but I also turn to movies, comics books, hanging out with my friends, listening to music and even going for hikes in order to cool my jets. There are lots of things I do to relieve stress, I don't always reach for my diapers and onesies. I love being a baby, don't get me wrong, but it's far from being my main source of stress relief, in fact, being an AB to me sort of transcends mere stress relief, it is a deep, personal and emotionally fulfilling part of who I am as a person (you may find that the same goes for you in relation to your DL and Little side). That being said, however, I still need to balance my AB side with my Adult side and having multiple forms of stress relief helps me to achieve this, it also makes my life more interesting, after all, variety is the spice of life.
So, yeah, it sucks that you only have tentative acceptance/understanding on the part of your Mother (you are quite lucky in that respect, my Mother absolutely flipped when she discovered my baby items, threw everything I owned out and shamed me to members of my family), but she does have a point, it's always good to have other interests. Maybe take stock of the things you like to do other than being diapered and turn to some of those if you want to lessen your diaper time at present. If you still want to wear your diapers, which is most understandable and well within your rights, then indulge in secrecy, diaper up in your room, on your own time and try to keep it private. Don't think of this as a purge, it's not, being a DL and a Little will always be a part of you and you haven't ditched your stash, maybe try thinking of or viewing this a chance to find some new hobbies and to bring some balance into your time as a DL.
Good luck to you
