Can't say much helpful other than regards the alcohol side...
First, it's very much a drug, like tobacco, caffeine, heroin, cannabis, etc etc etc.
It effects different people very differently. It can take only a year or two to become addicted, some people may take 10 years or more to become so. Some can stop without too much physical issue, some can die from the withdrawals in extreme cases. Habituation as opposed to addiction can still be very harmful. There is likely no totally safe amount, and even controlling units consumed may still be an issue (some binge drink once a week, binge drinking very harmful).
Alcohol though is different from a great many psychoactive drugs, cannabinoids, stimulants, opiates and opioid's, and many more operate on the body's cell receptors like a key in a lock to activate an existing process.
Alcohol, to be brutally honest, would be classed far closer (if not the same) as solvent abuse. It effects just about every part of the body in a negative fashion, and operates on the mind by preventing the brain from operating correctly in almost all it's functions.
The only reason alcohol isn't far more vilified like tobacco is the huge wealth generated from sales and consumption, and the powerful lobbying groups that funds.
My only advice I could give from my own substance misuse experiences is to try to analyse why you had a drink when you feel you needed one and couldn't control it (as opposed to having a pint with a mate in the pub - a controlled, minor consumption for positive reasons) after the fact. Understanding the reasons why your mind keeps following the repeated patterns can make self awareness of what you're actually doing and why far more focussed, and gives you something tangible to work on.
But proper support will give you far better guidance than I can, my little offer there is just a part of the game, not a complete solution. Good luck and don't be scared to fail or acknowledge percieved failure. Failure can be the most powerful of teaching experiences. Few if any get it right first time.