Self motivation is possible.If you have to win an exam just look to one who had won it.Try to practice like him , but before that try to understand your limitations.If you realise it you can take remedy steps and there by to motivate yourself.
I agree with pradeep. Reading books authored by great leaders teaches you how to tackle tough situations.When you are depressed due to your failure, these books prove to the best well wisher.
There are a number of ways through which one can motive oneself and sometimes by following the examples of others while at other times by thinking about one's loved ones....