I just completed 10K (6 miles), considering it has been 20+ years since I was on a bike, I think I did good. After I got over what I looked like in the mirror( I did that when I wore my first jogging shorts in years), I got out there.
At one point I was going to chicken out, then I decided to go for it. I am glad i have all the right gear(gloves, helmet and biking shorts, although I wore regular shorts over them), the only problem was I could not figure out how to attache my saddle bag, so I through it in my runners vest. I am glad I bought a good bike, jogging and biking are very different, you notice every pothole and change in grade much more. I followed the advice of another and did an active cool down, I got off the bike and did a slow and steady paced walk for .5k.
My heart was racing the entire time, I never fell off, i managed my stops and even had enough courage to go on one of the main roads where the speeds are 80K. I have learned that riding in 25K winds is a lot less fun until the wind is at your back.
After today I have to learn how to change gears better, have 24 options is a lot.
Thanks all for the advice, it went a lot better than I thought, I am glad I cut back on how far I was going to go for my first ride.