They can be our best friends, or our worst enemies.
They can serve our best interests, or sabotage them.
With every thought that we think (choose), the Universe goes into action by simply rearranging itself to accommodate our beliefs. It works on our behalf based on what we choose to think and believe. As energy patterns are rearranged, that which we think about most often (whether in a positive light or negative one) begins the manifestation process.
If you continually focus your thoughts on that which you don't want, those things will surely find their way into your life. Focusing your thoughts on your most positive possibilities enables you to take the steps to make those possibilities real. When you think positive thoughts, you'll be guided to take positive actions. When you take positive actions, you get valuable results.
Your thoughts determine and direct the actions that you take. Choose them as wisely as you would choose your friends.