Remember the first time you got stoned or drunk, or you had your first cigarette or did your first line of cocaine?
I'm sure you do.
Yet you don't recall anything else that happened that day.
This is because of glutamate. It aids learning and memory creation.

It always accompanies excessive dopamine stimulation in the Nucleus Accumbens.
This means the more potent your arousal or high, the deeper the memory imprint.
Over time, this turns into triggers & leads to hyper memory formation that makes you relapse

This is why cigarette smokers who quit have a nostalgic feeling towards their smoking days.. They think of it as the good old days.
Even though the nicotine is out of the system
The memory imprint remains