picking up the pace, but not long enough

so today's run was eh...when i was running i was going fast, i felt like i was going the speed i go sprinting, only without as much exertion. BUT i couldn't keep it up, obviously, and when i slowed down the pace to jog i felt awkward and uncomfortable, so a bit of walking. Tomorrow I'm going to run a mile straight through, NO WALKING. end of discussion I can do it!