It's hard to stay on my diet.

I've been having a diet plan outlined for months, and I've been on it for a few days on and off then I fail and eat bad foods again. The longest I've gone is about 5 days with just eating healthy. It's pretty sad, seeing that the diet is supposed to last 6 months for the smell to go away.

Anyone else have this problem? Any tips on staying on a diet? It's so hard. But I really want to get better.. :(