I'm just the opposite. I feel better after a ride (my work commute is 25mi r/t), and I ride at ~19-20mph riding speed, even though I'm a 'senior citizen' at 63+. I found that I feel better after a vigorous ride 45+ years ago when I was in college! I feel that it helps burn the toxins out of my system! Oh, and it is not simply a 'runner's high' since the overall good feeling 'high' lasts for a day or two afterwards.