You want to be positive and work at doing the impossible, let me tell you right now that is a tall order. To be positive and work towards doing the impossible takes a lot of work, something you must be willing to do everyday. Work at being positive, thinking positive, doing the positive and not giving time to consider the results of your efforts until you are well on your way.
Read positive self help books, anything that will help you work on improving your self and help you shape your environment. Speak to people as you pass them by saying something like good morning, have a nice day, Can I help you with that? Yes work at it like it is a job and pretty soon you will become as positive as you will like to be and you may find that you like the new positive you.