I never encountered it. All I ever met were temporary setbacks. We are not retreating - we are advancing in another Direction. There is no such thing as a problem without a gift in its' hands. Obstacles are those things you see when you take your eyes off your goal.
All life is an experiment.
The more experiments you make the better. What if you do fail, and get fairly rolled in the dirt once or twice. Up again, you shall never be so afraid of a tumble. Persistence and determination are omnipotent. The slogan 'press on' has solved and always will solve the problems of the human race.