Complete and utter frustration

I have hit some kind of wall, beyond which lies my goal.  I can't seem to go over or around it, no matter how kindly or urgently I ask my body to do so.  I am quite frustrated - sad, even - and it doesn't even make sense.  I'm not sure what to do.  I've invested a lot of time, energy, and pride into this, and I do not want to quit.  I will not quit.  I just don't know how to get over this wall.