Motivation is a very personal thing. What motivates you may not motivate someone else and vice versa. You must find what motivates you and concentrate on that.
You can think about how much better you'll look and feel after you lose weight. You can consider the work, dieting or exercise to be an accomplishment, use it as an excuse to treat yourself, probably not to candy though.
If you notice changes then you can really motivate yourself so look out for them. Feel your body, can you tell where you're losing weight? Think about what you will do when you look the way you want to look.
When you're walking up stairs note the point when you begin to feel tired or out of breath, note it again after a week or two and see if you can take more stairs before being tired or winded.
Small measuring sticks are very useful because they are the ones we can notice week to week.
