"Worrying too much about the past is called depression. Worrying too much about the future is called anxiety."
That's what can happen when you cheat on your diet. You are hard on yourself about the fact that you cheated on your diet and you worry too much about the bad effects it could have on you in the future.
At the end of the day, what is done is done. The one thing you can do is be your best, disciplined self from this moment forward.
Worrying too much about it often brings out a "What the hell?" attitude and you then continue further downward path--you do not want to go this route- in fact this is the key to dieting success; continuing despite a perceived set back
At the same time, unhappiness is something you can use to motivate yourself to get back on track immediately--and stay there.
You have to work out how your mind works best.
If I make any mistake I regret in my life, I immediately look at what my overall mission and ultimate goal is. Usually when I do something that doesn't fit with my overall mission, it is because I lost sight momentarily of what I ultimately wanted to accomplish.
Make the rules and stick to them. Just think of it a tool for reaching your ultimate goal. If you say no alcohol on a week day then that is what you have to do to get there. It is really no big deal.
Same as if you are jogging or lifting weights. Most balanced people don't really like doing these sort types of activities day after day BUT they are neccessary for what they want to achieve- so when you ARE doing them or saying NO to krispy kreme doughnut just visualise how good you are going to look in the future and that it will all be worth it. And it will be I can assure you.
Those are just some mental and emotional strategies you might try.
As far as dieting and and exercise strategies to compensate for cheating on your diet (like eating less food later in the day or extra cardiovascular training), I do NOT recommend these!
Because they really are not effective solutions as far as your long term plans are concerned.
More importantly, you do not want to "trick" yourself into believing that the temporary weakness you had is actually "no big deal" that can be compensated for later on.
That is the first step toward the relentless, subconscious process of a person lowering their fitness standards--and have no clue later on why they aren't achieving their goals.