I gave up smoking on the 27th of January 1999 and yes I gained weight.
I can remember that time very clearly, in fact I draw on that strength in other areas of my life.
It can be done and you can be one of those Ex smokers!
Remember what a very toxic drug nicotine is. David Bowie once said in an interview that giving up nicotine was harder for him than giving up heroin!
Sadly there are no magic answers or I would not be on this forum myself because I would be fabulously slim and rich!
The day to day refocussing of my goal is the approach I am currently taking and I wish you well in your journey.