Letting go of negativity and mental blocks? This is something I work with frequently. Have you ever tried meditation? If so, what kind works for you?
I have three things that might help:
1. Live cleanly. This means eating right, keeping a positive attitude, and "cleaning up" any negativity, physical or mental, in your life. Living a clean mental life is important here, so if you find yourself repeating negative thoughts such as "I hate myself" or "I'm worthless" replace them with positive thoughts such as "I have a lot going good for me right now" or "Life is tough, but I can do it". If you want to look into affirmations there is a page somewhere here on the Magicka forum that has a ton of them, but I forget where it is. As for physical cleaning, take a bubble bath or a nice hot shower and intend to cleanse your mind/soul as well as your body. I also find that spending a day cleaning my house can cleanse the soul.
2. Meditation of light: If you want to cast a circle or ritualize this that is up to you, but I'll keep it basic. Just sit in a comfortable position for meditation and visualize a sphere of pure, white light in your heart. Even if you can only visualize a tiny speck that's ok. Focus on how pure, holy and sacred it is, because it's your inner Divine light. Just visualize it expanding and focus on the light replacing and eliminating the darkness. See how big you can get it. If it takes up your whole body, then great! Keep that feeling as long as you can, and see if you can expand it into your aura and beyond. Even if you can't make it big, that's ok. Just focus on that white light and don't push yourself to make it too big too fast. If you have trouble with it you might want to do it in baby steps: Make a tiny sphere one day, and the next day make it a little bigger, and keep going accordingly. I forget where I got this from, and I'd credit them if I remembered where I learned it from.
3. Aura/chakra cleansing: Do you work with your aura or chakras? If not you might want to start, because cleansing here is important. Let me know if you're interested because there is a LOT out there on this.