What adds the most to your personality is your perception towards people, towards life. That can be achieved through positivity, better known as optimism.
It is very well said by Sandeep Maheshwari that many people mistake positivity as having good expectations and high hopes for any event that is to take place. Optimism is not that you give an exam and sit back, hoping for a good result.
But if you face any problem in life, and if you take it as a challenge rather than sitting there in the corner, crying about it is called optimism. If you work day and night for something, regardless of the result and of the name and fame you will achieve from it, that is optimism. Thinking positively means to be brave and happy enough to convert any difficulty into an opportunity. For instance, if you are told to speak up in front of a crowd, think that it is an opportunity to develop yourself and express your skill.
If said in a nutshell, optimism means finding the good in the bad. Everything possesses something good in itself. It just needs that optimistic perception. Whatever happens is always for some good.