Each and every time you fuck up should be a time where you learn.  If you're applying the knowledge gained from when you screw up, it will be very rare that you make the same mistake twice.  A flaw-free live is completely impossible, as much as the A-type personalities of the world wish it were so.  However, a life lived with integrity and purpose is as close as we can get.  Don't allow your missteps to prevent you from finishing your path, and don't allow your dirty shins and skinned knees to give you permission to sit down and throw up your hands.