Here at the beginning of addressing our thinking mind, we're going to start by simply learning to observe it. This can be trickier than it sounds, as for our whole lives thus far the monkey has been in control of our attention, rather than us being in control of it. We live our lives hypnotised by our thoughts.
You can't change anything that you're not aware of, but conversely, once you're aware of something, that mere observation itself begins a process of change. Your first task in harnessing your thinking mind is to watch and learn.
Employ a Breath of Freedom: 1-breath where you're aware of the breath itself, is all the leverage you need to retake control of your attention and put yourself back into the driver's seat of your mind...your awareness. From here, notice what your thinking mind has been doing, reset yourself, and make a decision about where and how you want to go back in.