I finished the C25K a couple of weeks ago and was delighted with my achievement but am struggling to improve my fitness level. I'm 54 and thrilled to be able to run for 30 minutes, I'm running at about 7k per minute so I actually run for 35 mins in order to complete the 5k. This morning was a disaster and for the first time, I had to walk for the last ten minutes. What's happened? I did have a drink of water before I went, could that be the problem, I usually just get out of bed and go.