There are times when I look at my half-marathon training plan and I think "how can I possibly run those times". It's easy to talk yourself out of a fast run or a track workout because of the fear of not being able to hit a specific time or pace. However, as I've learned over the past few weeks of running fast, sustained runs, you'll never know what you are capable of doing if you don't attempt. There have been days were I didn't hit my pace and it's okay because I attempted, I got out there, I ran and I learned. The runs that don't quite measure up are the ones with the greatest learning potential - what was your sleep like the night before, what did you eat, was it a different course or terrain? Use those runs as building blocks and remember, never let the fear of not hitting a pace stop you from attempting the run.