I recognise that we need some negative thoughts to keep us safe, but most negative thoughts are irrational and these are the ones that you need to dominate and replace with positive ones.
It takes 30 days to replace a habit, which is what negative thought patterns are, so you need to picture this image every day for 30 days.
I found a good way was to draw the images onto a piece of card and carry it around with me and I just kept looking at it regularly throughout the day. If you do the same, you will soon notice the difference in how you feel and act.
Stamp Out Those Irrational Negative Thoughts