Quitting is a tough thing.
It is so dam familiar that it's hard to let go. That and missing the dopamine release makes us think we can't go without it.
I had never experienced depression or anxiety to any extent until after I quit smoking.
I had a real rough time during the 50's (days 54/55/56 as I recall)
I felt hopeless. (Now I know I was in No Man's Land)
What did I learn?
I learned I didn't want to go through that again.
I learned "The only way out is through"
If you feel like you just can't do it, perhaps you might go to your dr and get an RX for a mild anti-depressant that you can get off of when you feel you don't need it any longer. Many of these take a month to begin working so use good judgement. They also take a few weeks to get off of.
start learning what other things release dopamine right up front.
and CHOCOLATE among other things.
Volunteering or a hobby that holds your interest are a couple of other helpful long term distractions.
"Quits don't stick unless you stick to them."