something that obstructs or hinders progress
This definition may be accurate, but it's unhelpful.
When encountering an Obstacle in life - don't think of it as something that obstructs progress.
If there's one thing I learned for taking part in a Spartan Race, it's this:
Obstacles don't stop you. They're just an indicator that one has to change their current way of progressing.
Obstacle courses aren't impossible - they're exercises, tests, tasks.
Next time you encounter an obstacle remember that your life is the obstacle course, and no obstacle course is impossible... But any good one is difficult.