I was a 30 year smoker, 1 - 1 1/2 ppd. I'd tried to quit using nicotine gum, patches, prescription drugs, and even hypnosis twice. Nothing worked for long.
I tried my first ecig, an NJoy disposable about 5 years ago. I was amused that one of these might just work for me. I was getting a dose of nicotine which my brain said I needed, and I was also duplicating the addictive "behavior" of the "hand-to-mouth" fixation and the "inhale/exhale" behavior which are all part of the addiction.
I was able to make a total transition within a weeks time. I vaped as much as I wanted. If I got a craving for a cigarette, I vaped more. If that didn't help, I allowed myself a cigarette....half of one, and saved the second half for the next time. Those partially smoked butts tasted pretty awful, but I believe that helped my craving for a cigarette.
Toward the end of the week, I was easily preferring my vape over the cigarettes. I never bought another pack of cigarettes after that, and haven't touched one in 5 years.
Of course, I upgraded my gear over time. I ditched the cigalike after about a month. Got a mechanical mod and some cartotanks. Then got a Provari. Four years into vaping and I'm now rebuilding coils.
Never have had a craving for a cigarette since I finished that last pack five years ago.
Edit: Upon recalling when I first started vaping, I must admit that I had extra MOTIVATION to quit smoking. The day I bought that first ecig, my mother found out that she had cancer. She was dead within two weeks. Her illness and death caught me completely off guard, and I realized then that if I didn't quit smoking now that I was going to follow her to the grave in short time. I think most people have to be motivated enough to quit; if you aren't there's a strong chance you will fail, like anything else in life that really matters.