Negative thoughts can be damning. One negative thought leads to another and by the time you realize a castle of doom is built. The dreamer fuses life into it and carries this monster 24x7. Peace of mind is forsaken but plans of how to beat the imagined demon occupies the mind. Thoughts of shame, of danger lurking, of failures and many similar thoughts make life hell.
The world out there seem to be so happy except you. It looks like it is mocking at your miseries. It appears that you have been hand picked for persecution. You have a tiny tinge of hope somewhere deep inside secretly wishing that your worries evaporate. Self pity and self deprecation becomes your favorite hobby.
Thoughts per se are neither negative nor positive. It is simply a manifestation that has occurred in your mind. Thoughts that are not to your liking are labeled as negative and those that make you feel good are seen as positive thoughts. What is positive thought to you could be a negative thought to someone else. You are a body of desires. Each desire seeks its fulfillment. You comprehend these emotions through thoughts. One part of you wants fulfillment of those desires and another part of it - your values, your constraints etc - stops it from happening. You are not sure what needs to be done to feel content. It seem to be never ending tussle.
Dropping desire is not possible because you didn't create the desire. It just happened to you. Suppressing desire is not going to be effective in the long run. It makes you desperate and vulnerable to irreversible mistakes. Working to fulfill won't end it either. You would want more of it - like more money, more recognition. So how do one be immune to negative thoughts?
A temporary solution is to wait for the change in tide that brings momentary uplifting thoughts. You can also attempt to force exciting thoughts that seem to bring results in the short term but know it would wear you out mentally in the long run. That's how positive thinking works. It is like an emergency medication not for daily usage.
Filling your mind with happy events of the past and promising future would temporarily disengage from the rut. You might probably be doing the opposite of what you are doing now. You might have to step out to the world, do small things that uplifts, meet happier and sensible people. These can pave the way for permanent solution but be aware they are more like breathers. The problem is in the root.
A permanent solution would be to understand yourself. Learn to look within to know why you desire certain things, why certain thoughts come to haunt you. The coming to know the reason behind them would point the right direction for the right set of actions. Work on the source than react to the situation on the surface. It takes commitment. If you are serious you would work for a permanent solution otherwise your want to be happy is only a wishful thinking.
Hate hates to forgive. Love loves to forgive. Compassion wasn't hurt to forgive.
Hate has mission. Love has purpose. Compassion has no agenda.
Hate hurts. Love soothes. Compassion heals.
