If you knew where your thoughts could take you, you would want to control them too.
The more we think about something, the more comfortable we become with it, the more likely we are to explore within it (perhaps beyond cultural norms). Sometimes this is good, sometimes it's not.
If you experiment for yourself, you will find that with many things, the more you think about them, the more you end up thinking about them, and eventually the more things you end up doing because of the thoughts you've had about it.
So if you want to become a teacher, just plant a small seed of thought in yourself, such as a question for yourself to ponder. For example, "Do I want to teach Elementary, High, College, or Something else?"
Nurture that small seed of thought by asking more questions and seeking out the answers. Those answers will prompt more questions and better enable you to complete the task you want, or better enable you to avoid it- which you would probably not want to do once you've invested a certain amount of time into it.
The same is true unfortunately for the things we don't want to do. The more we think about them and enable ourselves to feel comfortable with them, the more likely we are to do them. Although it is a thin line, it better enables us to avoid those things as well. Often times in my experience, it's not worth the time to learn avoidance techniques for some "unworthy" thoughts.
Unworthy thoughts often end up being a waste of time or more. Just think about winning the lottery, $200 million dollars. The more we think about the $200 million, the more we want it, the more we think about taking a chance to win it, the more likely we are to do it. Some gamblers out there (myself unfortunately included on an occasion), may now be itching for a ticket simply because of the thoughts of it just now.
You can avert thoughts though, you can even avert imminent actions. Just think a thought that is contrary to that action. For example - Instead of most likely wasting a dollar, definitely get a pack of gum with that dollar. Or instead of going anywhere to buy anything, get home just a moment sooner, or stay home! Save your own time by not spending that dollar.
Time is priceless as they say. Take a moment to consider not just your actions, but more uncommonly, your thoughts - And you may end up saving a lot of time due to situations you could have avoided.