Missed Workouts

I have only had to miss a couple of work outs so far and I have been able to shift the weeks schedule to accommodate them. However the more worrying thing is that in some I just can't continue at the proper pace to the end.

This seems to be mostly in the longer runs, however intellectually I know that I need to build up my base slowly, the emotional side of me, is like how the hell can I run a half marathon when I can't run 3 miles without walking? However a few weeks ago that would have been I can't run 2 miles without walking so I am improving.