How do I stop myself from texting him?

I would personally say, block his number, and then delete it. Tends to work pretty well, in my experience.

Delete his number - you can write it down, if needed, but this way you have more time to controll your impulses. Think about what you expect or wish as an answer - is it realistic?

To stop yourself from texting him you must keep yourself distracted. This can be done by socialising in activities.

you could distract yourself. go out with friends,go do a sport, or even just turn your phone off & watch a movie.

Try to make something to keep your mind bussy, look for a hobby, look for something that you like.

I wish I knew all the answers. I’m in the same boat and even though it’s killing me I have to do this. I know your hurting as I am. The only advise I can give is to think about your future and this time will pass

When I have the urge to text a guy that's not good for me I just put him on the block list. Because if he is the type to constantly text you until you reply than most likely you will give in and text him. With him being on the block list even if he messages you, you will not receive the message. And if you do decide to stop texting a guy make sure it's a good reason don't stop texting him over a petty matter if it's something you can fix. Don't make permanent decisions based on temporary feelings.

Anytime you want to text him, step away from your phone and use distractions. Accept that you want to text him cause if you don't accept that feeling then it'll just grow and grow and it'll get worse. If you feel you have a message for him that can't wait, then write a letter or phone a trusted friend who will listen to what you have to say to him. That way it's all out of your system for the time being. If you still feel that message needs to be sent, maybe wait another 24 hours or write out reasons why texting him is a bad idea. You are stronger than you think.