To know yourself is half the battle. Knowing your personality type can give you a clue as to the type of work environments you prefer working in or how you tend to deal with people. If you are a natural recluse you probably don't want to work the Reception desk.
There are a number of free personality test online. One of the ones I tested was Typefocus. There is a list of 66 questions that you need to answer. When you are finished you will be told your most likely personality type.
You might not like the things that you learn about yourself. For example, in one of my descriptions indicated that I like starting things more than I like finishing them. That is true but I do finish 90% of what I set out to do. The 0ther 10% I get detoured by something more interesting.