When you’re already feeling bad, have you ever found that other things get you down a lot easier than they normally would? This tends to be the effect of negative thinking, that it has an impact on the way we see just about everything in our life.
It’s true that bad things can happen to just about anyone. However, people aren’t happy only because bad things never happen to them – it’s the way that they look at things that creates our happiness.
How to Stop Negative Thinking and Believe in Positive Thinking
The first thing you’ll need to realise is that we all have beliefs, most of which come from other people. These can be things like ‘life is hard’ – they are negative and they unconsciously shape everything we think. You need to start by, instead, coming up with your own beliefs that will serve you.

Using Affirmations to Help
This is hard for many to do, which is why it’s become so popular to repeat affirmations, to reaffirm what your logic is trying to tell you, but what your emotions still need to be convinced of.
Repeat these affirmations over a period of weeks, and eventually you’ll start to change your thought patterns. But remember: negative thinking does not go away instantly, and it does take work.
Affirmations are one of the easiest ways to make something a true belief, simply by repeating things to yourself over and over again. Over time you’ll stop negative thinking almost permanently!

Source: http://www.howtothinkpositive.com/negative-thinking.html