Alcohol is a mood-altering substance. It affects the nerves that transmit messages to the body by slowing them down and the more alcohol you consume the greater the effect it has. The reason that people usually become more energetic and "cheerful" when they have a drink is that alcohol affects the parts of the brain that are responsible for self-restraint. As you drink, alcohol passes into the bloodstream.
Ethanol is the ingredient of alcohol that induces intoxication and its molecules are so small that they fit into the gaps between brain cells. There they can affect the neurotransmitters that allow all brain activities. If you drink fast, the alcohol will flood the brain.
Your reactions are slowing down and as you drink more you may end up without coordination of movements or without balance. Your speech can get confusing and you may start to see double. If you have consumed a large amount of alcohol you may also have strong emotional reactions manifested e.g. violence or crying. Because your judgment has faded, you may be doing things you wouldn't normally do, from dancing on tables to going home with a stranger. These may seem like a good idea at the time, but they can be extremely dangerous.
So if you realize that - you or a friend of yours – have these signs, reduce or stop drinking immediately. The last thing you want is to lose control.