It's been about a decade since I last rode, and in trying out bikes today, at first there was an unexpected period of not feeling sure what I was doing (hello, doing things that scare you), but I got the hang of it.
Having purchased a bike, I was gonna just walk my bike home, since I'd left my helmet at home, but I was nearly at Davis when I decided to just ride.
The hardest thing is telling myself to own the lanes -- my instinct is to ride close to the right, to stay out of the way of vehicular traffic, even though intellectually I know that's more dangerous.
Dealing with traffic is also difficult/scary. I am proud of myself for biking the Powder House Rotary (I considered getting off my bike and walking it through umpteen crosswalks).