White knuckling not overspending

I’m struggling not to spend money on things I don’t need and don’t plan on buying. I’m going through the 30 day spending tracking in the Money course and I have a little over a week to go. I’m finding that it was easier for the first two weeks to be disciplined and lately I’ve been very tempted by high end online purchases. I feel a lot of pain when I realize it’s not in my budget to do something and I haven’t quite identified why. I’ve been tempted very recently to say screw it and buy things anyway. I think I’ve done well, but I feel like maybe I’m not doing the work I need to do on myself in order to make these urges go away and stop having them. Thoughts or advice?