I will add my voice to the chorus - I absolutely feel much better after the first half hour or so of running. For my last half marathon, I actually ran negative mile splits for miles 9-13, and I didn't feel all that bad when I finished. That race convinced me that a marathon was possible for me

I ran a fast-for-me 5K on the treadmill on Monday. On Tuesday, I got a couple of immunizations, so my bike interval workout that night was only so-so. Then, I had to skip my run yesterday because I felt so awful from the shots (chills, fever, tired, blah!). I did another 5K on the treadmill today, and I'm moving my long run up to tomorrow because I'll be on a plane flying to Costa Rica on Saturday!