How do you keep a promise to yourself?

I just felt like blogging for once. It has been a while. But I'm on my phone so not how long it will be. So i havent really lost any weight since November which is very very discouraging and causes me to cheat more. I was on Nutrisystem until January. It worked very well but i didn't feel very good and i was hungry and tired all the time. Since then i have been doing the primal blueprint diet. (Google marks daily Apple). Even though i havent lost any weight I've never felt sooo good. I have more energy and i sleep better. The food is very delicious. But i don't have time with school to do the proper workout. (I havent really worked out since November). And the food isn't cheap. And this stresses my finances. So im not sure what to do now. I keep telling myself i won't cheat, but i still cheat everyday. And in march i gained 5 lbs.. I could use advice. But on another note, im making A's in accounting, econ, and algebra. I don't know my grade in history but im sure it is a F.. I don't know what it is. I just hate history sooo much. I tell myself not to skip the class but i do every time! Why am i not stronger?