I use Matt's calculation for position sizing. I calculate a dollar amount that I'm willing to risk and enter my positions that way. 

Here is the direct link to that education: https://bpt-videos.s3.amazonaws.com/trade_to_win/trade_to_win.html

Also, take a look at the rest of the education that is provided on the website here: https://breakpointtrades.com/education/

I became a member because I wanted to learn from those more experienced than myself with results to back it up. I remain a member because being around everyone here makes me better. I have my views though I'm willing to be wrong in trading and in life because it will eventually happen. This is another important big lesson. Willingness to be wrong and change my view if needed has improved my results. As is preached here often: Protect, Monitor, and Adjust. 

Finally, I used to overtrade and watch the screen all day. The first thing I did before coming back to smaller timeframe trading is I would only take action when the systems took action. Exactly as the alerts were sent out. This kept me from selling a good position too soon. Moves take time to materialize and it can be uncomfortable sitting in a trade with drawdown, though its rare to get a swing trade perfectly to the nose on entry and exit. If someone can do that consistently my hat is off to them. I certainly cannot try to call a top or bottom in price, though I can apply supply and demand principles to improve my risk/reward proposition. 

This post this morning is me preaching to myself, so I hope in some way it has answered your question and helped you as well. I appreciate you.