What are your goals? If you don't know why you want something, it won't be as important for you to get it. By focusing on positive goals (such as "I want to feel fit and energetic" rather than “I don’t want to be this tired and stressed”) it will be easier to visualise them and you will be more inclined to work towards them.
The ultimate cure for lack of motivation is results. If you can maintain a positive attitude and keep up your exercise programme, you will soon be spurred on by the changes you see and feel. Leading a happier, healthier life and watching the body you have always wanted develop before your eyes can be incredibly motivational and empowering.
When a lot of the foods you love are prohibited, you are likely to feel unhappy and deprived (which is by far the easiest way to fall off the wagon). To help avoid this trap, allow yourself a little of what you like each day but do so in moderation. Savour each bite and feel good about it. You are then better equipped to get back to your healthy eating plan without feeling guilty or resentful.