For me it’s will power. I’ll explain!
I don’t have any ‘won’t power’: I found I very difficult to say ‘I won’t have a cake, thank you’. Now I use will power. I tell myself that I will stick to keto, that I will lose weight, that I will be healthier and, now I’ve been doing it a few weeks, that I do feel better. I hardly look at all my previous go to foods any more! I struggled to get carbs down the first week but since then I’ve been aiming for 20g carbs and been under most days, with 25g being the highest. I had to use protein shakes with double cream to start with, as quick and easy breakfasts or lunches but now I rarely use them as I’m not usually hungry until about 11am.
You can, and will, do this, just have breakfast and find you version of my will power!