You would be hard pressed to find someone successful who does not believe in himself. It's imperative that we all draw from this belief to overcome all the setbacks, because if there is one thing that is certain, is that they will happen.
Learn to celebrate your wins, it's so easy to surrender to the idea of the losses, the things that don't get done, the things that don't work out, that we forget all we have achieved. Every step forward is a step in the right direction, and no one who wants to be successful should play the short game.
The best selling author Jon Gordon said once, "Talk to yourself more than you listen to yourself." It sounds silly at first glance, but the idea is quite powerful. Instead of thinking of ourselves as victims, we need to be our own life coaches, our own motivators and remind ourselves that no matter how hard thing get, we can do it... we can overcome, because we do believe in ourselves.