You cannot predict or determine with 100% the outcome of your life, but you can steer your course in life.
Steering a ship
If you’re the captain of a ship, you can steer the direction of the ship but you cannot control externals (the condition of the sea, whether there are pirates in the sea, or the weather conditions). It is your duty as a captain to be brave, to exercise your best judgement, and for you to steer boldly in a certain direction.
When you’re steering your ship of life in a certain direction, you cannot control whether you will be hit with turbulent waves. However you can direct the general course (direction of your ship).
I feel we can use a similar metaphor in life:
You can generally steer your direction in life, but you cannot predict or determine the outcome.
Thus it seems the optimal strategy in life is to steer as wisely, boldly, and bravely in life — and leave the rest to fate. Think of the saying:
Throw your spear, and leave the rest to Zeus!