Fighting the "I Can't"

"I Can't" is an argument I fight daily.  With kids who still want you to do it for them.  With new people at work.  With my head, it tries to define my capabilities.  Pinpointing the problem is that I tend to be self depreciating.  Tend to?  Ok, I am.  I have a lot of negative self-talk. 

I had a rough time of it this morning with my tempo run.  5 minutes warmup - 35 minutes fast - 5 minutes cooldown.  In my mind, I still can't run over 5.3mph without gasping for breath.   In reality, I can push a lot harder for that for an increasing amount of time.  I have a hard time wrapping my head around it. 

This morning, I did the tempo portion of the run at 6.2.  I wasn't overly exerted.  I finished the tempo portion and still felt like I could keep running.  I even felt a little disappointed in myself that I could have pushed harder - but didn't.  However, for the entire run, I struggled to push down the "You can't do this anymore" thoughts.  Several times, I reached to lower the speed because, well, I don't even have a good reason why I wanted to lower the speed. 

The struggle to be 'good enough' in our own mind is so hard.  Thin enough.  Fast enough.  Smart enough.  Why is it so hard to be worthy of loving ourselves?  At what point, are we holding ourselves back from obtaining the sucess we want - in life, in athletics, in love, in careers, in whatever - because we're so busy mentally thinking we don't deserve it?