There are a lot of tedious art exercises that you have to do if you want to improve your drawing. It's kind of like jumping rope or hitting the hangy ball thingy if you want to be a boxer: it's not exciting, but to build your skill/speed/stamina/accuracy, you have to do it.
In between working on delightfully secret Christmas commissions, I've been doing cast studies this morning. You look at a cast (or in my case, a picture of a cast) and you measure it and try to get your angles right, and you try to reproduce it as faithfully as possible. This means spending several hours (sometimes 30 or more) to do a really, really accurate cast drawing.
I like to draw quickly, then move on to the next piece, so I broke after just 3 hours, 1.5 on each, and I know they have some problems. So I'm going to try again in a day or so and gradually work up my stamina.
Anyway... If you're out there, trying to improve at art and staring miserably at some boring practice, like mannequinization or measuring or perspective studies or whatever it may be... It is totally worth investing your time and doing the work to the best of your ability. I see my own stuff improve in tiny increments after each practice session, and while I still want to be a lot better than I currently am, I'm far better than I was at the start of 2015, and I can't wait to see how much I improve over the course of 2016.
Exercise courtesy this Noah Bradley video, cast from a Charles Bargue plate.