I will lose/destroy my purpose of coming here if I do not see him.

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. The main purpose of me of coming here tonight is to see him. My purpose to come here will be destroyed/will be gone if I do not see him.
  2. I will lose/destroy my purpose of coming here if I do not see him.
  3. I do not want to destroy/lose my purpose of coming here.
  4. It’s your perception of love that lengthen you life is not so much about the physical attraction.

Are the above sentences correct?

2

I would refine them and say:

  1. The main purpose of my coming here tonight is to see him. The purpose will be defeated if I do not see him.
  2. I will lose/miss my purpose of coming here if I do not see him.
  3. I do not want to miss/lose my purpose of coming here.
  4. It’s your perception of love, not physical attraction, which lengthens your life.
3
  1. My main purpose for coming here tonight is to see him. That purpose will be lost if I do not see him. (to avoid ‘see him’ twice, you could say ‘… if he does not put in an appearance.’)
  2. If I do not see him it will have been a waste of time me coming here.
  3. I do not want to lose the opportunity for which I came.
  4. It’s your perception of love, not physical attraction, which lengthens your life.

Your original 2/3 are odd because you do not really ‘miss a purpose’. You ‘have a purpose’ but ‘miss an opportunity’.