Things keep getting in the way

On Friday I ran with the friend who is training for a half marathon. She had done a 7-mile run the day before and was up for an easy 4.5-mile run with me. Her easy pace is faster than my race pace, so it was a good training workout for me. We did a loop by my house that I'm pretty familiar with. In fact, I had just biked it last week. We started out fast, going down hill. I felt pretty good, but after about 1.5 miles, I started to feel some cramps coming on. I tried to ignore them, but when we got to a hill, I had to stop and walk. After about 5 minutes of walking, the cramps miraculously disappeared, and we were able to pick up running again. I guess I'll have this to deal with for about a week or so now. It's a good thing I didn't pre-register for a race today, which I had been contemplating.
It's a little frustrating that things like this keep getting in the way of my training. If we had kept running all the way on Friday we may have averaged 8-minute miles. If I can't set the right pace myself, running with her is a great way to get used to the speed, but I hate having to slow her down or stop and walk. In any case, our time for 4.5 miles was 43:51, which is 9:44 pace.
Yesterday I had to work and took the day off from running, so I'll probably go for another run today, although I might stay in and use the treadmill, or, depending on the weather, I might take the bike for a spin. We'll see.