Lots of great advice here about stepping down.
I agree------don't over-think it. I started with a high nic juice 13 months or so ago, and leaned on it very heavily in order to kill any urge for a cigarette. After just a few days, I was able to back off of vaping frequency with no urges at all for a regular cig. Within just a couple of months, I stocked up on a few 18mg juices. Same procedure------leaned on it heavily at first if I had any screaming urges, finding that after a few days I was able to back off on the vaping frequency. Tho I haven't used it myself, I like the idea of having 2 set-ups with higher and lower nic for those times when a bit of an extra kick would be helpful. Same principle ---- just use more vapor to kill off those urges.
The biggest key for me, I think, was KNOWING that I now had something that would completely kill off those killer urges to smoke a real cigarette, and KNOWING that I now did not need anything else. I just knew in my head and heart that it was just a matter of vaping more or less. I now also know that the odds of me going back to analog smokes is next to nil, as there are just too many tasty vapor flavors that I really enjoy.
I'm now down to 0 nic, keep a supply of 0 and 6mg, using 0 most of the time, and the 6 mg mostly at parties and gatherings, and occasionally at night. I find going back and forth to be easy, and I have no dramatic urges for nicotine when using the 0 that I am aware of.
Just keep at it, and DON'T GIVE UP! I'm sure it can be easier for some than for others, but I'm positive that you can and will eventually get to whatever nic level you want!