I'm not in a position to say people have failed me, because I'm the type of person who barely expects anything from anyone. While that could be partly a lie based on the human theory of unconsciously doing things for the benefit of it, still, I do as much as I can to not let "expectations" stare or break me.
As life goes on, and we get to learn more and more about responsibility, we'd realize most of the things we do are affecting the people around us, and as a result, it's notable that our closest company could let us down sooner or later. Life has a way of trying to bring us down, but faith and determination keeps us going.
I'd love to use the "human legs" as a point of discussion. We see it as a tool of functionality, yes, it is, without it, processing of certain things becomes slower or not possible in some cases. But as a famous quote says, "if you can't fly run, if you can't run walk, if you can't walk crawl, no matter what, just keep moving" In the case of running a race, when a runners legs get weakened, he or she tends to stop, but in the race of life, same methods shouldn't be applied.
The legs in this context isn't really referring to the physical legs, it's somewhat a metaphor in this expression. Your legs could be your closest friend who seemed like he or she would always be there, who seemed like forever was the goal, or there was never gonna be a giving up, but suddenly got tired. The legs could represent your parents, your teachers who have concluded that you can't learn anything, that your brain isn't compatible. None of them should have the final say and thought, their decision shouldn't be what determines the outcome of your life. It isn't generally easy to keep going when you lose those factors, it's always like losing your motivation, but what we fail to understand is that we are the greatest motivation to ourselves.
One shouldn't rely on the support from others, let your faith in yourself give you courage, let your courage bring about determination to push forward. When your legs go numb and stop walking, cut them off. When your tongue stops speaking, cut it off. When your hands stop carrying your loads, cut it off. Anything that was there, but then suddenly stopped working should be cut off. They are all in the past so they shouldn't influence the presence. Keep the ball rolling any means necessary, because unlike the Game of football, there are no rules saying only your legs are allowed to score a goal. Every motion brings you a step closer even without your legs, so if your legs stop working, abandon them.