See it as a step forward. Starting again or starting over does NOT have to be seen as a failure. You can see it as a step forward, a step UP! A failure would not be starting over at all!
Get a partner. Find someone to tackle your goal with you, find a friend who will be strict to hold you accountable to what you want, email them your progress, be open to constructive feedback, help them help you!
Take small steps that stick. Don't try and change your life in ONE day, take a few small steps to start. Pick a small step today and DO it. Build on that, literally, small single steps will cause you to go far. Drink one more bottle of water, make that phone call, stand up for what you need today.
Get HELP! Enlist the help of a trainer,a specialist, an online course, something you can go to for help in the area you are working on. You won't feel alone then and you will be able to tap into support and advice.
Do what you enjoy. If you enjoy the change you make, then you will be less likely to go back on your new path! A new diet plan? Add in a little of your old faves, a little seasoning etc. I became a trainer because I loved working out, in turn I love helping people realize their dreams.