

Consider the externalities. Fighting, drunk driving, alcohol-facilitated abuse of all types, and the impacts on everyone who has to mop up afterwards. Oliver Wendell Holmes Hr. said “The right to swing my fists ends where the other man’s nose begins”, and in that light the only time consuming something that takes away your capacity for rational thought is even remotely acceptable is at home, alone, locked inside.

A lot of it is the nervous system. The nervous system has two divisions with complementary functions: the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS). The SNS activates when the body is under stress, and the PNS activates when the body is at rest and unstressed.
The reproductive system is activated by the PNS (haha). When all is well, performance is good. But if you are under stress, due to lack of sleep or life events for example, performance is not going to be nearly as good.
In your case, your body is receiving things it is not meant to handle. Our lungs are designed to breathe plain old air without any additives, and water is the healthiest thing we can drink. Sugary drinks and nicotine can give you short bursts of energy, but it’s not sustainable. When the energy wears off, you’re worse off than before and it’s stressing your body. By cutting back on smoking and sugary drinks, you’ll put less stress on your body and activate your PNS more, which leads to better well-being all around and improved performance.
Be sure to drink enough water. You can tell if you’re drinking enough water by if your urine is pale and straw-colored. If you’re craving something sweet, you could try fruit juice or an Arnold Palmer instead! Cutting back on or quitting smoking is more complicated, but it can be done with the help of your healthcare provider. You can talk to them about what options are available. In the meantime, part of what makes smoking addictive is the sensation of a cigarette in your teeth, so perhaps chewing gum can help satisfy that and help you smoke less. Your mileage may vary, so this is still something to speak to your healthcare provider about.