Whatever you believe to be true, becomes your thoughts.
Whatever your thoughts are, they become your words.
Whatever words you speak, become your actions.
Whatever actions you take, become your habits.
Whatever habits you have created become your values.
Whatever values you possess, become your reality.
If you are not happy with the friends you have or significant other - change your thoughts.
If you are not happy with your career and coworkers - change your thoughts.
If you are not happy with your home or living space - change your thoughts.
If you are not happy with yourself - change your thoughts.
If you are not happy with the way your life is right now - change your thoughts.
Understanding the way your thoughts play on your life is huge. Because your life right now started with a thought. Take the "change test" and write a list of all the things that are not working in your life right now. Then ask yourself, about each item: What thoughts first come to mind when I think of _______? It's a good bet that the thing in life that isn't working out well - just had a negative thought about it. And then that thing that had a negative thought - was spoken about negatively. And then those negative words turned into action and those actions became a habit ...
The best way to change your reality is to change the way you think about it.