My advice would be to try to improve your line quality, so you can find one long line instead of scratching a ton of attempts. Now, that is easier said than done, and will take some practice. To understand the concept of line quality I recommend drawabox.com, at least the first few lessons before it goes into actual perspectivic drawing.
And then, do a lot of short drawings, a minute or so, but still try to take your time for every line. That will lead to a lot of badly measured figures with really wonky proportions. Don't try to correct them, just do the next one, but try to focus on controlling every line. You won't get your figures "finished", that is OK, that is not what your goal is. You will feel a lot of frustration while doing that, and that is a good thing. Frustration is the emotion that occurs, when your cortex tells their neurons, that they don't do their job the way they are supposed to, in other words, that is how learning a new skill feels on a physical level.
You can look into some short measuring techniques, like finding three dots on the reference in a straight line, just to compare distances, or looking for vertical or horizontal relations, but a lot of measuring will eventually have to run in the background of your mind, while you focus on a thousand other things while drawing. Repeatedly drawing the human body is also kind of a measuring technique, as you get used to the proportions. But for now, your measuring just isn't there yet, and it is more useful to accept that and improve the line quality instead. Your figures will look wonky for quite a time to come, but if they are at least drawn with clean, long, and decisive lines they will already look a lot better.
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