Or am I just imagining it? Is it the nicotine that gives you a boost?

I sincerely doubt it.

Oh sure, the nicotine gives you a quick "buzz"; but this is only temporary........Nicotine is rapidly degraded by the body, and loses it's effects after at most 20 minutes, after which you are certain to feel even *more* depressed than before.

Depression, anxiety, nervousness, acute stress, etc, are all well known effects of nicotine withdrawal.

That rapid "crash" afterward is part of what drives people to keep trying to get more nicotine, and become addicted.

It is an open secret that tobacco companies put a large number of additives in their cigarettes, a practice which the government legally has no control or oversight. Many of the additives are designed to both increase the rate that nicotine is absorbed into the body, and also to increase the rate it is broken down and removed. This produces an extremely rapid "spike" of nicotine, which encourages addiction. Tobacco companies are actually just part of the "nicotine delivery industry",(to quote an inside memo from Phillip Morris)

Fortunately(for the tobacco companies), nicotine is also extremely poisonous and acts as a nerve toxin at even moderate levels. Due to it's nasty side effects, nicotine is usually self-limiting.

This is not true of "hard" drugs. Most laboratory animals, (and humans), if given an unlimited supply of highly pure Methamphetamine, will keep dosing themselves until they OD and die. If they are given a choice between food and meth they will choose the meth until they starve to death. "hard" drugs are not "self-limiting."