Alcohol is so widely used that its legality can be thought of as somewhat independent of its mostly alarming effects on the body. It's important to understand alcohol from the physical perspective to appreciate its psychological component. In this post I will address the basic pharmacology of alcohol. I think this is an important piece to understanding alcohol in general.
There are also a couple of blood alcohol content level calculators that are available online that deserve mentioning - they are free and relatively accurate so long as you have an idea about how much you're going to drink.
The basics - alcohol is not merely a depressant
Alcohol is a depressant. This represents a significant portion of our understanding of it, at least on a day-to-day or conversational level. However, it is a unique depressant given its euphoria-producing properties. Euphoria, characterized by a sudden onset of excitability and confidence (possibly over-confidence) is quintessentially indicated not in depressants but in psychostimulants (that is, "speed"). Thus for alcohol to have euphoria-producing effects is hardly intuitive.
How is it that alcohol causes euphoria if its a depressant?
A quick review of empirical literature on the pharmacology of alcoholism contains frequent indications that "the exact mechanism is not known" - though that saying is hardly specific to alcohol per se.
In any event, alcohol influences the activity of at least four major neural systems: the NMDA receptors, GABA receptors, Dopamine receptors, and the opioid receptors. There are certainly additional effects, however it is the influence on the dopamine receptors that interests us here because it is likely that system which is responsible for the euphoria associated with alcohol.
Dopamine is a neurotransmitter that, when manipulated, can be associated with diverse behavioral effects including addiction, euphoria, pleasure, psychomotor repetition, and cognitive enhancement. Alcohol appears to influence dopamine receptors in the limbic system. If you think about the times when alcohol has made you apt to be more emotional than what you consider to be normal, this might be a physical explanation.
What are some tools for monitoring alcohol's influence on me?
Of course the most important thing about alcohol is that you know its effects. This goes beyond simply knowing how it behaves as a drug. It also requires proactive action that indicates such knowledge is being put to use. A simple awareness of your blood alcohol level (BAC) will suffice.
You can use a blood alcohol calculator online so that you can prevent a problem. As long as you know roughly how much you're going to drink its reasonably accurate.
Another tool in this regard is your friends and family. If someone you know voices a concern about your habits, try not to take it personally. Chances are they are simply concerned. They may not be as accurate at estimating your BAC, but they may provide what makes it possible for you to think about that in the first place. Social support is absolutely key in managing alcohol and alcohol-related health concerns.