Negative thoughts

Because when one is thinking negative thoughts, one is bleedin' miserable.

Everything depends on what does 'negative reasoning' mean?
Stating out the problems for example is not negative reasoning (although the people with personal complexes often view it as such), and vice versa - closing your eyes to the problems and to the injustice by remaining passive and indifferent is in no way positive reasoning. Talking the things that are convenient and that suit you is not positive reasoning, and talking the things that you think and telling the truth (whatever it might be) is not negative reasoning.
Besides I am not sure that happiness is the goal of life. If mum is happy with the SUV by destroying the planet in-between ... and at some point in time her successors would be forced to wear gas masks when jogging in the park ... how much does this 'happiness' worth?
Moreover when a person is happy he is continuously annoying the people around him (especially the ones that feel unhappy) and the trolls are mobilized to interfere your happiness ... at full power.

Thank you guys for your answers.

"U cannot afford the luxury of a negative thought."

If by 'negative thoughts' you mean 'intrusive thoughts', maybe you should identify of what type: inappropriate aggressive thoughts, inappropriate sexual thoughts or blasphemous religious thoughts.
If this is the case, the negative thoughts are not hindrance to you happiness ... these thoughts are hindrance to your health. Consult with a professional.
If by negative thoughts you mean common cognitive distortions like: all-or-nothing thinking; making hasty generalizations; filtering: focusing entirely on negative elements; disqualifying the positive, etc. ... this is a problem of behavior and habits. Consult with experts in the field.
If by negative thoughts you mean simply pessimism or melancholia: some people are hopeless pessimists, others people are hopeless optimists, but the worst case scenario is to be indifferent. Some people are of the opinion that the melancholia is even positive feeling.
Happiness is not a top design artwork - to model it and to copy and paste it from somewhere. Happiness is a state of mind ... and narrow is the gate and long is the way to achieve it. BTW the approach to be applied case-by-case is very personal and specific.