Down-heartened...who am I trying to kid?

So...when did the change happen? Monday I got on the treadmill and did my pathetic little half hour walk/run to try and turn me into a runner. I did okay! 'I'm getting this', I thought 'Maybe there's hope after all?' I wasn't counting every second of the one and a half minute run (okay laugh if you want, it SEEMS longer!) and the time went quickly. 'I could do that again' I though proudly. Maybe the 5k run isn't such a fantasy after all. (Don't get me wrong, I don't enjoy running, not in the slightest, I have my own personal reasons for needing to try and do this.) So today, on go my trainers and my ipod. LMFAO burst into song and off I go again. So what happened? Today my legs ached, my chest hurt, my breathing was laboured, I wanted off! I still completed the task before me but couldn't wait for it to end. Is it time to face the facts? I will never be a runner? I will just never measure up.