I've never taken meth, but I was addicted to amphetamine several years ago. The drug is chemically very similar and the effects are basically like meth, just less extreme.
The first time I snorted the stuff I was hanging out with friends who took it. For whatever reason they weren't able to get any that day, so I offered to pick some up for them since I knew a guy who sold it. I wasn't planning to try any myself, but ended up doing so anyway. At first I would take it simply to be able to get by with very little sleep and have more time to do stuff after a long day at work. Then I started taking it before and at work too because without it I'd be to exhausted to do my job. Eventually I just took it out of habit and because I was addicted. I was also very depressed at the time and it helped to numb the intrusive thoughts I was having. It didn't take long for my addiction to be a major contributing factor to my depression and feelings of self-hate (I was just a worthless junkie afterall).
I went through phases of wanting to quit and phases where I didn't love myself enough to care. Eventually it got to the point where I realized that the negative effects from my addiction far outweighed the suffering my depression was causing me. I hit rock bottom both physically and emotionally and wanted to quit, but didn't feel like I was able to or that it would be worth it. I frequently thought about suicide as a way out. In the end I did muster up all my strength and quit. It sucked. The withdrawals were a nightmare. I probably slept easily 16+ hours for the first week after quitting and didn't feel physically normal again for about 3 weeks. The emotional damage to longer to heal.
I was probably spending around 1000€ a month on drugs (speed, alcohol and weed) and despite being able to hold my job throughout got myself into debt that took around 3 years to pay off.
I'm natrually underweight and lost even more weight. I weighed 52kg at my lowest. I looked like shit from complete exhaustion and had little strength to do anything. My nose was completely fucked and I'd get nosebleeds regularly. One time I was in the shower and a got a nosebleed an piece of flesh came out with it. Blowing my nose would produce a non-stop supply of foamy snot mixed with blood. The inside of my mouth and my throat was permanently sore from the caustic effects of the speed and biting my tongue and cheeks. Eating was painful and my teeth were constantly sore from grinding. Those physical effects were the biggest contributing factor to quitting. Psychologically it contributed majorly to my depression and led me to some really dark places. I'm not sure my depression had ever been as bad as it was then and it certainly hasn't been since. Behaviourally it didn't really cause any problems. I never stole or commited crimes to feed my addictions and by some miracle was able to hold down my job. I was fairly good at hiding it, but anyone who knew anything about drugs would've noticed pretty quick.
I didn't get addicted from trying it once. That took a while. But the first time taking it certainly got rid of any inhibitions I had towards taking it again and in the end I think you can say any addiction starts from trying something for the first time, even if it takes a lot longer to actually get addicted. I didn't expect to get addicted, but I definitely noticed what was happening before it would have been too late. I kept using anyway, partly because I was too depressed to care about my own wellbeing and partly because I underestimated just how shitty it would be to be addicted to speed.
As for today? I haven't taken speed for years. I quit cold turkey and relapsed two or three of times in the first few months, but the relapses didn't result in me falling back into my old ways. Rather I'd regret it the next day and go back to trying to get sober. I did go through a phase where I experimented with a lot of psychedelics (mainly LSD), but those drugs aren't really addictive and if anything I'd say they helped me. The last few years I haven't really been doing that either. Not because I made a conscious decision not to, I just kind of lost interest and stopped without thinking about it. I still smoke a lot of weed, but I don't really see that as a problem since it doesn't interfere with my life and I feel like I'm a responsible stoner (not at work, when I have to drive or when I've got shit to do).