I started C25K 6 weeks ago. I've just completed my 2nd run on week 6 and I had to cut it short. Granted it was only by 1 minute, but a minute is a long time in running especially for me. I completed the 20 min run without stopping I was pleased with myself and so happy, but the last 2 runs have been such hard work, my body feels more tired and I'm finding it harder to catch my breath and these last 2 runs have had walking breaks. I don't understand? The first run of week 6 I told myself it was because it was 1°c so I was freezing and I had finished a 12 hour shift so would of been hard, but today I've had great sleep. I ate perfectly yesterday and had a rest day. I don't know what I'm doing wrong and I was so upset with myself for cutting it short but my legs was killing and my chest was tight. Any advice?