Tolerance to nicotine is unlike other drugs. Obviously that doesn't mean that it's not there or doesn't exist, quite the contrary the tolerance builds quite rapidly for new users. However, unlike other drugs, this tolerance does reach a plateau within a week or so. So what does that mean? That means that after a week the high and extremely calming effect of nicotine fades away, but instead leaves way for something much more useful. The residual effect left for each nicotine dose after on will last on for the rest of your life.
Many heavy smokers use 1 to 2 pack a day very steadily for the rest of their life. You never hear someone who smokes 10 packs a day and accidentally does an overdose. A pack generally contains 25 cigarettes and every cigarette around 1.5-2mg of nicotine. Despite the high availability of cigarettes and its addictive nature, overdose from cigarettes is unheard of. That is because past a certain point, every dose still does the trick and there is no point in taking more and the user knows it. There are few other drugs that have this property. Nicotine is very addictive, but is not a drug that has an abuse potential. Even chain smokers who smoke literally a cigarette after another such as Walt Disney don't get problems related to nicotine; rather it's the smoke who takes them, unfortunately. Replace the smoke with a lozenge, and you have something completely harmless; still addictive, but harmless.
As discussed earlier, almost everyone can benefit from using nicotine in their everyday lives, but the way cigarettes have been characterized in last century (and rightly so) and the fact that the main active ingredient in cigarettes is nicotine, the perception of nicotine by itself is distorted to say the least. The human mind is quick to make links, even if they're wrong. Despite all of this, cigarettes remain legal. That's fine of course, we live in a free society where is as long as you don't harm other, you are free to do whatever you want. The problem is when you get advice from people who clearly don't know what they're talking about and think they should decide for you what is bad or not. The only way to know how nicotine works is the way one would approach anything, through reading and research.