I am a life-long regular donor. I have learned that I need to donate early in the week as I generally take my longer rides on weekends. I once got terribly sick on a hot ride 2 days after donating and realized that, with the heat and distance of the ride, my body needed all the red blood cells it could get and it was still down several. I tend to get winded a little more easily for about 1-2 days after donating. Your mileage may vary. It's a great thing to do!