I finished C25K Week 4/Day1 this morning before work, and it wasn't as bad as I thought, but it was still pretty challenging! The run intervals were longer than the walk intervals (minus warm up and cool down), which was work for me. I'm still a little tired from it, but okay to get through the workday. Of course I have class tonight! I think I'll be sleeping well again.
I've been using a different app from the initial one. This one was created by Active.com, the creator of the "original" C25K program, so it goes for the whole 9 weeks. The other app I tried was an 8-week program. Check out more information on Active.com's app here.