How to restart your diet? DECIDE to. It really is that simple. You tell yourself that enough is enough already. No more excuses. No more nonsense. No more pushing it off till "tomorrow". Start doing what's required, what's necessary - today. And every day.
This is no hardship - living a healthy lifestyle. It's a blessing and a joy. It's not something to dread, but to embrace and celebrate.
And like's been said already - staying on plan gives one a incredible sense of control, ESPECIALLY during times of stress. It IS the one thing that we do have complete and total control over.
And I'm sure you know the rest - get rid of the junk, add in healthy foods, plan, plan and plan some more. Track your food, journal, etc., etc., etc.
But none of that can or will happen, unless you DECIDE to do it. Decide to do it and then commit to it. Once and for all and no matter what.