I know exactly what you mean. FWIW, after being diagnosed with high blood sugar with a very high A1c, and being overweight with high cholesterol, and smoking, the priorities were to get the weight down, lower the cholesterol, and get the blood sugar under control.
Three months ago I weighed 299, now I'm at 251. (That's 48 pounds in 3 months. Even I'm impressed by that one, and I'm a hard SOB to impress.) A1c was 11.3 and now it's 6.2. Cholesterol is dramatically better, but not yet down to my goal (which I forget what it is, but rest assured my doctor has not). Smoking has gone from 2 packs a day down to 4 packs a week.
I'm not yet walking like I should be, but I've done what I've done so far with a dramatic change in diet. I've found it an easy change, considering the alternatives. I'm not even the least bit tempted by the stuff I shouldn't eat.
If I can do it, there's no doubt in my mind that you can do it, too. It's easier than you think. Calm but determined.