Shot me, now!

I had a great week in the gym this week, but my body didnt recovery as well as i thought it would on my Sunday rest day. Monday I was very sluggish and had a huge lack of energy which hit hard at Kisado Monday night. Half way through I had to stop and take a break because I thought I was going to faint. Last week I hung in there with the best of them but yesterday it was like a smack in the face that I had NO ENERGY.. I got really hot/cold at the same time and felt sick to my stomach. It was so aweful. I walked to the side and took a couple minute break to slow my heart rate and to get a drink of water. It was the WORST feeling in the world not being able to compete. Im so competitive and having to step aside while others were doing just fine about killed me. I am so embarrased, I am second guessing going back Wednesday. I apoligized to my instructor last night because I felt like I had failed.
How can you get over this feeling even though you were just listening to the limit of your own body. UGH!!
But I do have TKD tonight and hopefully it will cheer up my spirits some.