I still suck at double unders

WOD

Unbroken double unders in sets of:

5-10-15-20-25-30-35-40-45-50
45-40-35-30-25-20-15-10-5

(there was a 100m running penalty for messing up on a set larger than 40, then having to start over from 5. Of course, if doing singles, double the reps)

I remember at the beginning of the year, our box did a list of resolutions for the next year, where everyone wrote a fitness goal they wanted to improve/achive.

Mine went something like double unders, a faster mile, unassisted pull-ups.

I haven't achieved any of these yet, but I guess it can't also be denied that I'm getting better at all these things little by little.

For the  first 10 minute we did mobility, then some 5 minutes of technique drilling for double unders.
Most people did the wod by modifying it to singles; but I used the reaming 25 minutes to practice double unders. My goal was to get at least the first 5 unbroken set.

Utter failure.
The most I could do was 4, and that was with single-double, pattern. I started to get so frustrated I wanted to curl up and cry in a corner. The only other girl that also trained her doubles, whipped out a set of 10, but this was the most she could manage. This was really good thou, cuz her form was great! Whenever I do doubles I have a tendency to jump backwards, the coach says that this is what's ruining my timing.

Because the girl coach was there (yey! morning class) and she let me use her wire rope, I swallowed my sadness and kept at it until the timer ran out. Coach D also gave me a LOT of pointers and said to keep training consistently and I will get it.

But yeah, how much additional time can I add to my training if I really want to become good at "all the things"?