How can I know God's will for my life?

You must realise that the very word test implies a strain—it implies a strain even to the breaking point—but because God is in command, the breaking point is never reached. 

At that stage, the Shepherd steps in, and gathering His little flock into the safety of His Arms bids them forget. Apply this if you can  to the details of your daily life—to those important happenings, which have a way of going wrong in spite of your best endeavours. 

Detach yourself sufficiently from these incidents to say—It is but a test and I will take it in the right way.