In any endeavor, there are factors outside your control that affect the outcome.
Sometimes that outcome will not materialize at all, sometime you will only get part of what you were working towards.
To create a mindset where you are still in control you need to think in terms of bets.
A poker player who has a great hand may still be beaten by another hand. If he views his outcome as a chance to win in which he is willing to bet on, in the long run, he will win.
It is the same in investing. You invest in a set of stocks where you believe each stock has a chance of making you money. As long as you are right more often than you are wrong you will make money and therefore be in control of your investments.
It is the same idea in life. Work towards a number of outcomes where the sum of all the outcomes will move you forward even though some work and some don’t
With this mindset of understanding and reviewing the chance that any one of the outcomes you are working towards may or may not work, you can start to formulate strategies to maximize the overall outcome.