Looking for motivation

Hard week. I did finally exercise on Tuesday. I walked 3 miles and ran the last half mile. It was so hard! How on earth did I run a half marathon just 2 weeks ago, and running a half mile was so hard. It probably didn't help that I hadn't eaten well at all that day. I WILL exercise today. I have to get back in the groove, but I'm having a hard time finding the groove. I've eaten bad every day this week. I am actually looking forward to Saturday's run as well, even though I know it will be hard, but it will be good to hopefully snap myself back into routine a bit.