eight is enough!?!?

As an aside...does anyone remember that eighties tv show?
This week has been crazy difficult to run. My C25K program is kicking my butt. It's been relatively easy to increase my running time each week and now it's just going to kick into high gear and I'm afraid I'm not ready for it. This weeks schedule: 3 days of 5min run/3 min walk (done), 3 days of 8min run/5 min walk and then the dreaded 20 minute run!!! Cereal? Yesterday's 8min run/5min walk kicked my ass and now all sorts of aches and pains just seem to leach on to me like barnacles while I run. Am I pushing myself to much? I really want to be at this point but it's so difficult! And by no means am I giving up but it's been so long since I've done anything like this that I'm not sure how "painful" its supposed to be. Yuck, I feel like a complainer...
Regardless, lets hope today's 8 min runs feel better than yesterday's runs.
Also, I tried to run with a smile (a suggestion from my brother) for the last minute and it was totally awkward and I'm not sure I liked it. It takes a lot of energy to run and smile...not sure I'm there yet either. All of my effort goes to keeping one foot bouncing in front of the other.