1) Sustainability - Can you sustain and endure what you're doing for the rest of your life? Yes, the REST OF YOUR LIFE. If the answer is no, then get ready to lose weight and gain even more back. Whether its diet or exercise, you need to assess if this is something you can keep up with. Sure we can wake up at 4 am, work out before work, and then hit the gym again after work. But how long can we keep up with this? If you can't see yourself being able to keep your routine the rest of your life you're better off reassessing and coming up with a better plan.
2) Stick to a Routine - Put yourself in a good routine and stick with it. Repeatability is a good thing and the more we're able to continue a routine (ie. working out at 6 am Monday-Friday or not eating after 8 pm) the easier it is for our body to adapt and be okay with it.
3) Go slow - Don't feel the need that you have to go 110% everyday on your diet and exercise. It goes back to #1, if you can't keep this pace up for the rest of your life, find a new way to go about your weight loss goals.
4) Something is better than nothing - Don't make your workouts an all or nothing ordeal. If you don't have it in you to your run that morning 5K, try walking it or running a shorter distance. Remember...baby step.
5) Don't get down on yourself - Its okay if you miss a work out or cheat on your diet. The important thing is to not allow that to spiral into a string of days or weeks. If you slip up on your exercise or diet, simply pick up where you left off.