Don't worry if you slip. Just keep on vaping and hit it harder when you feel the urge for a cig. It will go away. If it doesn't, then go up in nicotine level until you find the point that keeps you from wanting tobacco. 24mg is good, but some find the need to start off with 36mg.
I went from 40 cigs a day, sometimes more, to 6 a day the first week I vaped. I continued smoking those 6 a day for two more years. I had two with coffee, one after each meal, and one before bed. One day, I decided not to buy the next pack. There was no urge, no craving, and no nervousness. I just vaped a little heavier for a week and then leveled back off.
It as much psychological as it is physical. You don't have to quit cold turkey. Just let the vape take away the cigs in its own time. I could have quit cigs the first week, but didn't know that. Still, it doesn't hurt to take away the psychological craving by having one or two a day when you are transitioning to vapor. Try giving them up after a few weeks and you might find that all you needed was your ecig anyway.