Wow, its crazy how much captaindammits story sounds like mine, exept for the fact that I started snorting instead of smoking. I started off using very rarely, maybe once a week or two, then days just kept sneaking their way in. I told myself this stuff isn't that great, its a backup if I run out of weed and I'll just keep it around to sell. Let's just say from that point it only took me 4 years to completely ruin my life and I consider myself to be a rather aware person, I just ignored all the signs because my ego is too strong to admit defeat to something.
All it took for me to go down the toilet was a rough spot in my relationship, a ball of dope, and my first noticable withdrawls (I guess I'll factor in one of my good friends at the time that shot the stuff too, but at that time I was ready to try it anyway). I didnt even know what was happening to me, you may actually have experienced them and blamed it on something else. One other thing, smoking is about the least potent route of administration, so I would think tolerance would raise even quicker. If you wonder if what you are doing is a problem, it is, don't doubt the only person you can trust, yourself.
The only reason I'm clean right now is because I got myself in a legal jam amongst many others and I know I need to fix some things and dope will get in the way. I miss it everyday like a woman or something even though I know how far down its taken me, its sick. This is coming from someone that has done a great deal of coke, crack, crank, ecstasy, acid, scripts of all kinds, pretty much every drug on that planet, and I've never had a habit I couldn't break until heroin. Its just not worth it, it may have been fun, but now I forever hold that fun on a pedestal, unconciously raising it above anything else. Its physically, emotionally, and spirititually draining on an unconcievable level.