I'm not sure I can help with motivation as it is something that I lack. One thing that I have found helps is to look at the details rather than the whole. Even the smallest thing can change things for the better.
Make a list of everything you would like to change. Break those down into smaller goals. Figure out what you need to do to accomplish each goal.
For example, maybe you want to eat less junk food. Your list would look something like this.
1. Eat less junk food
- throw out any junk food in the house
- don't buy any more.
- buy healthier snack food (granola bars, fruit, yogurt, etc)
Give yourself a few weeks to get used to each change before moving on to the next. Once you've accomplished one goal,
reward yourself. My suggestion is to pick something before you start that will keep you motivated. Something that you would be unlikely to buy or do otherwise. Like a really expensive yarn or a massage.
Just remember that you don't have to do it all and it's okay to slip up and have a bag of chips or a chocolate bar or whatever. You're allowed. I've heard that people who allow themselves a mistake every now and then are more likely to achieve their goal than people that don't.
I hope that helps.