1. Realize you have full control and decision of whether or not any of these negative beliefs, thoughts, or negative situations effect you, therefore if you let it effect you it is your own fault. Take full responsibility, ask yourself, "do i want this negative thought to ruin my whole day?" If you can concept this, you can easily make the decision to let go. Keep practicing and it becomes habit, until you no longer have them.

2. "Give it to your spirit guides/angels or higher power to take care of." Every time a negative belief/thought comes, or even a worry of your future, remember to just give it up, and let the higher powers take care of it - you don't have to, you just have to live in the moment and be receptive. the higher powers will steer you in the right direction, if you give up your control to them.

3. distantly, be aware as if you are looking at your thought from outer space and have no attachment to it put a stop to attaching any more unnecessary feelings to it, for example none of "oh my what a horrible thought". You only want to be aware of it, not add more onto it.

4. re - brainwash yourself. Counteract all negative thoughts, with positive thoughts, and stick to it until you reprogram your mind and get into the habit. Sometimes our thought forms are just a result of constant society brainwashing and our upbringings and things we program our brain to believe. The best way to defeat this, is to counteract and reprogram your thoughts, and change your beliefs into something more loving.
Take a look at how many unsupportive beliefs you have, example: beliefs that you are unworthy, fat, or the gloomy environments get you down. Believing you are depressed and can't do anything about it. Take a look at what your parents have pushed into your mind from your childhood and how that has resulted in your beliefs. Take a look at what kids in school told you that has resulted in unsupportive beliefs, take a look all over your life, what you see on television, everything that plays a part in your negative beliefs. Become aware of all those things, and counteract them. You can change your beliefs. When you do, since your mind governs your body, you can change your body, and how you react and see everything. Know that you are the master of your realm.

5. Practice positive affirmations.

6. Know that Love diminishes all negative. When love is near, no fear, no ego, or negative can exist. Boost your self confidence, be connected to Source, or to nature, and surround yourself in love.

7. Meditation. Quiet your mind. When you meditate, no thought forms can exist.

8. Purge your shadows by analyzing the root cause. After every negative thought assume it is your fault your ego talking, and try to pin point where the negative belief comes from. It always comes from somewhere. (even if it's just from society )

9. Let go in writing: Write up a list of all your resentments, fears, and all your character defects. Write down everything you have a problem with, and go through and analyze each and every one in point form, what the exact nature of your wrong is. Don't play the blame game. And don't feel shame. For example if you are mad at someone and they did something wrong, you take responsibility for how it effected you and made you feel, without getting into shame and putting yourself down. Did this situation effect your ego, your self security, your self confidence - there are many "self" words out there, the point is, how did it really make you feel. Hint: whenever we react strongly or negative to something or someone it means we are threatened by something. Doing this, you just may find some roots to your negative thought processes.

10. Forgive. Part of self awareness and taking responsibility for your own thoughts, forgive yourself, forgive others.

11. Crystals. Certain crystals can aid you in diminishing negative thought processes.

that's all i can think of right now, hopefully some of these steps help. I personally did all of those things, probably more that i haven't thought of