I always remember a friend of mine when he used to go to the mountains with his kids. After walking for a while, when the hill was getting steeper before reaching the pinnacle, the kids would start saying they were very tired and could not keep walking.
He used to tell them, "when you feel you cannot walk anymore, you have just used 10% of your physical capacity so stop complaining and keep hicking".
Most of the time, we believe something is impossible just because we do not have the patience to search for options or to go through the effort of trying to reach the goal.