As I said before, I did switch part for part of my investing to mechanical actions over time. This ensures that I always do the same in the same situation. When there is a lot of action it helps to stay calm and do what historically was the best to do in that situation.
Money management is a very important part of any investment strategy. It answers questions like how much to invest in a single position, how much initial margin, how much maximal margin, how much to add to positions, how much to sell from positions. It does however not answer what stocks to buy.
In my high risk growth-momentum strategy I use a minimum of entry price or actual price plus cash as the base. Unrealized gains are not included, but unrealized losses are. One position then is a fix percentage of that number, actually I use 6%. I allow a margin of 150% plus the difference of the actual S&P500 to the last all-time high. Meaning after stocks go down I can buy more, when they went up less.
Then I calculate the “unbalance” from the base value that does not include unrealized gains and from the actual value that includes them. The formula is just margin multiplied with that number plus cash minus actual value. That gives me two numbers, the money I can use to buy stocks or have to sell stocks if it is negative.
If one number is negative and the other positive I just sell for the same amount I buy. If both are negative I sell immediately. If both are positive I don’t sell when I buy the next position.
After one year of holding I sell a fix percentage of every position.
After a windfall profit of 500% I sell a fix percentage of every position. I did a table with percentage numbers to sell 20% and still have the position growing a little, it starts like “500, 1000, 1500, 2000, 2600, 3300” and so on. I’m sure there is a formula for that, but I did never reach to more than 2000% gain in any position. 
The money management reflects my personal situation, I need to take out money from time to time. In the savings phase of your life you may want other rules.
You may have seen that I never actually hold a positive cash saldo. One of my mottos is “cash is trash”, it does not produce anything and has a state-guarantee to lose value. But of course I need money to live, I spend EUR, CHF, USD and sometimes some smaller currencies. At least of the three big ones I have reserve cash for a year and therefor hold debt in at least that amount. That way I have no problem with inflation, the value of my money goes down (or up in case of deflation) exactly the same amount as the value of my debt.