My body no longer tolerates alcohol or caffeine

Reddit patient description: 23M, 5’7, athletic build, very active, no relevant health concerns aside from what is described below.

I am pretty in touch with my health. I am active, watch my nutrition for the most part, and occasionally take breaks from alcohol, marijuana (edibles), and caffeine. I decided to cut marijuana out indefinitely because the cons for me were outweighing the pros. I do not miss it at all, so that currently isn’t a concern of mine, I just wanted to paint a picture. I took a 3-month break from alcohol that started in August, followed by a 2-month break from caffeine starting in September. It’s the holiday season, and I have many loved ones visiting that like to go out for drinks. I decided that a couple or few nights of responsible drinking scattered throughout this holiday season wouldn’t be too detrimental to my overall health, so I gave it a shot Thanksgiving Eve. TERRIBLE hangover followed that I was paying for days after. Lightheadedness, significant fatigue, weakened performance in the gym/cardio sessions, etc. I took it easy to recover, but this past Saturday, I went out to the bars with my sister and our friends to celebrate her graduation. Same thing happened. I properly hydrate and take electrolytes to prepare and recover from a night out, eat a healthy amount of satiating foods prior to drinking, and refuse to drink two or more days in a row. It just seems that my body no longer tolerates any alcohol. This leads to my question; can abstaining from alcohol cause your body to build an intolerance to it?

Same thing for caffeine. I took the break because I realized my tolerance was getting a bit high, causing my intake to increase, inching closer to the limit of recommended intake. The withdrawal process was grueling, but I made it through. I was doing fine without caffeine for the weeks after, but I tried to introduce it after the nights of drinking (with black tea so my caffeine intake didn’t make a significant jump), slowly working my way up to one cup of coffee after breakfast. I have noticed that my heart health rating on my Garmin watch has decreased and I have been experiencing heart palpitations frequently throughout the day (the single strong heartbeat, the one that feeling like a thump in your diaphragm). This leads into my next question; can the body grow an intolerance for caffeine after a period of abstinence?

p.s. I am willing to cut these things out for the foreseeable future. I thankfully do not have an addiction, nor do I feel like they are a necessity to get through the day or have a good time during a night out. As I stated before, I am pretty in touch with my body, so I just wanted to gather more information on the why behind my body responding to a reintroduction of these things so I have a better understanding! Thanks in advance :)