I smoked a pack a day for about 15 years. I quit 7 1/2 years ago. I had quit for about a year, a few years before after watching my mother die of lung cancer. Not even seeing that will last for long if you're not ready.
Wanting to quit, and being ready are two different things. I made a promise to myself to quit the year I turned 30.
Note that I didn't set a quit date at that point, just that at some point that year I would be done. I did a lot of preparation in my head. Then I used the gum, making sure to follow the instructions. The key for me however was that I quit while on vacation from work. It changed my schedule and usual patterns.
They say it takes about a week to get all of the nicotine out of your system. After that it's all psychological. That (as you can tell by the stories here) is the true challenge. Getting over the psychological addiction. That and pretzels. I nibbled on a lot of pretzels for a few months
Good luck to Blas and anyone else thinking about quitting smoking. It's a challenge that is for sure.