@Happiness For You,
Happiness For You wrote:
How negative thoughts is hindrance to happiness?
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.