You usually do not win against sin by pretending you are stronger than you are. Humility starts with being honest with God about where you struggle and asking Him for help before you fall into the same thing again. Sometimes the best way to say no is to walk away, change what you are looking at, stop the conversation, leave the place, or avoid the situation that keeps pulling you back.
Being humble also means remembering that you need grace just as much as anyone else. You do not have to think badly about yourself to be humble. You simply stop acting like you have everything figured out. Admit when you are wrong. Ask forgiveness when you need to. Be willing to listen. Give God the credit for the good in your life.
When temptation comes, you can simply say, “God, I need Your help right now.” Sometimes that short prayer is enough to help you choose differently.