Kevin,
It is practice that will give you the confidence to step up to the easel and begin working straight away. Just keep showing up and paying attention. At some point it won't even occur to you that what you're trying to do is difficult, because you'll have done it successfully so many times.
In my experience, most of drawing is editing, and until you get some marks on the paper -- your "rough draft" -- there's nothing to edit. I don't know if you're using any kind of plumb lines or other measuring techniques, but it may help you get stuck into the drawing if you can just quickly but accurately mark off, say, the top of the head, bottom of the feet, and a few intermediate points (bottom of the chin, elbow, navel, top of the knee caps). To do that, you might take along a length of thread that you can hold out horizontally at arm's length to get these readings from the model and see where they need to go on your paper. You can let the thread hang vertically (use a washer or bit of kneaded eraser for a weight) and get some quick readings about the relative horizontal placement of various points and areas. ("Is the navel to the left of the back of the neck, or to the right?") Then you're ready, after only a few minutes, to start connecting the dots.
That quick check on where the top of the head and bottom of the feet land on your paper is also useful to avoid the problem you had regarding placement of the easel. If you're working sight-size (there's a discussion of the methodology
"here") , placement of the easel is critical. And even if you're not working sight-size, getting the top and bottom limits of the figure marked on your paper straight away will ensure that you don't wind up with a splendid little drawing but with no room for the feet.
Other artists are more comfortable with preliminary, loose strokes defining the basic gesture, which is just another way to quickly get something on the paper. What you put there will be correct or it won't be -- the only two possibilities -- and if it isn't, then you're all ready to decide how to correct it. But you can't get started until you get started.
Cheers