BE AWARE OF YOUR UNIQUE TRIGGERS
Whatever you habit is, you probably have specific situations in which you engage in your habit (at a certain time of day, in conjunction with another activity, when you're with a specific person). The first step to breaking any habit is to identify what these triggers are and avoid (or transform) them if possible. For example, I always seem to bite my nails when I'm alone and when I'm reading. It's something I do mindlessly, without even really thinking about it. Obviously I can't stop reading, but I could be more mindful of what I was doing. Every time I found myself putting my hand near my mouth, I'd quickly return it to my book, making sure I was holding the book with both hands at all times. Keep in mind that your triggers will be unique to you so you can't just go looking them up online; you have to pay close attention to when and where you engage in your habit (then you can search online for some ways to tackle the trigger if you can't think of any ideas).
RECOGNIZE WHAT'LL MOTIVATE YOU.
For decades I've longed to stop biting my nails, particularly in recent years when nail art became such a fun, creative trend. I'd always searched for some sort of motivator — an upcoming event, the start of a new year, etc. — to inspire me to quit, but nothing really worked for long. It wasn't until I thought about signing books (my dream come true!) that I really buckled down and felt motivated enough to attempt breaking my habit for good. No matter what bad habit you're battling, I bet you there's something out there that is better than the habit, something you'll receive (like pretty nails, for me!) that will make all the trouble of quitting worth it. It's not always easy to find a motivator that will keep you going, but don't give up. There is absolutely something that's worth quitting for and once you find it, it'll be the inspiration you need to keep the habit broken.
ENCOURAGE YOURSELF WITH LITTLE REWARDS.
Though I don't have a ton of extra money to spend, I know how important little rewards are to keep me motivated. (After all, my love language is gifts.) In order to keep myself on track, I'm giving myself little treats along the way, including manicures, new bottles of polish, and even some custom nail decals. These little rewards keep me interested in staying on track and they serve as reminders of my progress. If you don't have something directly linked to the habit you're breaking (like pretty polish for nail biters), try rewarding yourself with little things that make you really happy (and make sure those things are also positive for you — you don't want to go breaking one bad habit only to begin a new one!). These rewards need not be big or extravagant, but they should be things that you don't get or experience every day, things that will keep you inspired to keep going.
ASK OTHERS TO HOLD YOU ACCOUNTABLE.
I've found that letting others know what you're up to can really help you stay on track with breaking a bad habit. I've told my close friends and family members that I'm trying to stop biting my nails so that they can inquire about my progress (or simply look at my hands!) and I've even asked my boyfriend to tell me to stop if he happens to see me taking a nibble at nail. Telling others about what you're trying to do makes it feel almost as if you've made a promise to them as well as to yourself, and I've found that it's hard to break promises to others than it is to break them with yourself. If you have someone looking out for you, supporting your choice to break a habit that serves no positive purpose, you'll be more likely to stay on track.
KEEP YOUR DISTANCE FROM TEMPTATION.
The further away you keep the temptation, the easier it is to break the habit. Of course, when it comes to something like nails (which are always with you!), this can be really tough, but I've made it a new rule not to put my hands near my mouth — not even just to get that one tiny hangnail! — which makes it easier to resist biting. It's not always easy to do this — just as it won't always be easy for you to keep your distance from whatever's tempting you — but the more space you put between yourself and what tempts you, the more the temptation will lessen and the easier it will be to break your bad habit for good.