1. Set a minimum time frame, like 30 days or 90 days, that you will commit to this change. If you hate it by the end of that time period, you can think about changing or stopping. But you probably won’t. Habits take time to form and once they’re formed, they seem way easier and more normal.
2. Find a tracking or reward system that works for you. I like MyFitnessPal because I have friends on there who are potentially watching what I do, and that’s motivating for me, as is the gamelikeness of trying to “score” under a certain amount of calories every day. Maybe you need to make a chart and put a gold star on it for every day you do well. Maybe you need to buy a new Lush bath bomb at the end of every week you succeed. Maybe an hour of exercise = an hour of reading for pleasure. Figure out what’ll work for you, perhaps through trial and error, and then do it.
3. Remember that you don’t actually need motivation, you just need to do it. Even if you don’t feel like doing it, do it anyway and it’ll be easier once you’ve started making that healthy meal/running on the treadmill/whatever. No one moment is unendurable; no one craving HAS to be given into; no one bout of laziness HAS to be heeded. You have willpower, so you don’t always need motivation.
4. Find meals you love and exercises you love that will fit into your new plan. You won’t stick with it if you force yourself to eat or do things you hate. You have to love or at least like every element of your new lifestyle change for it to stick. Experiment with different ways of preparing veggies; try out various kinds of workout videos on YouTube; etc.
5. Have an idea of why you’re doing this (want to look and feel good for a particular event? Want to feel strong and capable? Want to make your ex jealous? Hey man, whatever works for you) and post some reminders of this reason in places where you might be likely to make food- or exercise-related decisions (on the fridge, next to the yoga mat, etc). Maybe you could post some motivational quotes or maybe you could make a vision board of what you want to achieve.