Motivation

I have a hard getting motivated to do work outs. However once I get started I feel so good that I just don't want to stop. WHY??
Today I went out and mowed the lawn. I just about had myself talked into counting that as my exercise for the day. {I know lame.} However I then decided that since I was already dressed I may as well run to. My 5k is only about 2 weeks away and I am not sure that I am ready for it.
I was going to go run outside since Ryan was home today. My boys however threw little fits about wanting to go. My double stroller currently has a flat tire and so I couldn't take them. So I jumped on the treadmill.
Seeing how I keep telling myself that I'm not going to be ready I was quite surprised today when I ran for 12 minutes at a speed of 5.0! I did a mile in 13 minutes. Now if I can just get to 3 miles and then maybe 6 and then I will think of a 1/2 marathon. Not so sure that a full marathon appeals to me.
So...I just need to keep that motivation that I feel while I am working out and the feeling after I am done. That "I ROCK" feeling! I'm not sure how to do it. Maybe I just keep doing it and one day it won't be so hard to just do it!