Im not much of a fitness expert or anything but for me it was repitition and perseverence, honostly.
I used to do like 30 max, then I would do that everynight, and sooner or later I started to increase by sets of 10 until now Im doing a good 80-90 max. s2g!
I usually play a little trick with my head, I found out that counting straight from 1-30 is really hard mentally, so, I do # sets of 10.
So like 220.127.116.11.18.104.22.168.9.10
..22.214.171.124.126.96.36.199.9.10 and so on
Also, if youve overcome your problem, and have gotten used to a certain amount, you can try either adding weight, or elevation....
just works for me, I dont know if its good or not