Thomas clued me in to Oliver Senior's instructional book on drawing hands several years ago. It is called How to draw hands, and the first sentence and paragraph is "This is an instruction book." I purchased a used copy and have had it around for a while. I recently did a drawing course on line with a delightful teacher, the Spanish illustrator Puño, who recommended drawing your own hand on successive days, so I am doing that now. I'm on day four.
When I look at the drawings, I see that they give me information. Most of the information is about how bad I am at drawing. I say this non-facetiously: I know what my hand looks like, and I know what a good drawing of a hand looks like, so I get very concrete, objective, and detailed feedback about where I've gone wrong. Once in a while, some small detail will be not horrible. I also know how much time and effort I've put into a particular day's work. At some point I will want to use and eraser and try to correct things and arrive at some less rough approximation.
The thing about the hand is that we are familiar with it, we have a model close by (my right hand, since I draw with my left), we can draw it in real life size, or even trace in on paper, and yet it is difficult to draw all the same. That is, the difficulty is not due to a lack of familiarity, but to the fact that in some sense we are not seeing it as it really is.
Since I don't expect myself to be able to do this well at an early stage, there is no negative emotion around the information. I could even give myself some jocular grades, like D plus plus or F triple minus or C flat minor.