The human body is a magical, unbelievable, frustrating, complex, irritating, beautiful machine!
If you are doing everything you're supposed to be doing and yet you are not seeing the results you desire, that is not a reflection on you. That is a reflection on your process.
Often persistence pays off...But it's hard to know when to persist on the same track and when to shift trajectory.
Regardless, it's OK to be frustrated with the process, the program, or the strategy.
But none of that means that YOU are a failure.