I think about my next meal or work out.
That sounds kind of odd... let me clarify.
I say "Well, poo. That sucks. I shouldn't have eaten that. Now I feel slumpy..." Then I think "Okay I've gotta get back to doing the right thing or I'm just gonna continue to feel slumpy. What's my next meal? Dinner? Okay what do I have planned? Baked chicken with spices, brown rice cooked with chicken broth, and steamed veggies with lemon pepper. Sounds good. I'll stick to that."
After the next meal and/or workout I feel... back to normal. Usually pretty guilt-free.