One problem you are having is you are trying to figure everything out with your mind ... that won't work.

You are also trying to see the whole picture to the end of your life on this earth ... that won't work.

What will work is to do today what God shows you to do.

And to talk to God ... asking what HE wants you to do ... this is continual ... learning to talk to God about all your fears and doubts as they come to your mind. .. 

You don't have to figure out everything to the end of your life on earth.

All you have to deal with is what God wants you to do today and doing that which God has shown you to do and to keep doing daily that word which God shows you.

This is how you get to end of your life.

Do today what God shows you .. This is the only way it will work.