Hazrath Ali (R.A) said thought is like a seed sown into your brain if you encourage the same thought again and again and make it powerful then that seed will develop into a strong well built tree.

So have positive thoughts and develop only positive thoughts and not negative ones.
If you want to have a command over your continuous running thoughts then don`t give any attention to negative thoughts and avoid watching hearing and looking at negative things and even avoid reading negative issues. If you give power to positive thoughts and let go and just dispose of all negative thoughts at the same time they appear in your brain then this habit will make you one day a winner. And practically a positive winner who will vibrate soothing healing and positive energy like a light wherever you go.
Sometimes negative thoughts run so continuously in your brain that you fail and become depressed instead of doing this you can dispose of the running continuous thoughts continuously.
Have a will and become a strong fighter:
If you have a strong will to dispose of all the negative thoughts at the same time they get inside your brain then you will win.
Sometimes thoughts do not leave you they echo and run so continuously and bother you a lot it is only at this stage you have got to become a continuous fighter. You have to fight these negative thoughts continuously and become unstoppable when you do this no one can and nothing can fail you.
For developing positive thoughts and getting rid of those continuous depressing thoughts you must read my ebook Popeye Spinach to the Soul.