I've been to two concerts so far, both metal shows, and I did surprisingly well. I was really freaked out that people+noise sensitivity+strobe lights+unfamiliar situation=disaster, but it went fabulously. I always carry a hat or something to cover my eyes just in case, but I didn't have any issues. (I also had my hands full with a toddler who also had a great time at both the shows we went to.)
Tip: I'm guessing Katatonia is going to be in a small club (I've heard of them), so try to find a place in the back, near the bar. I usually hang out there, because I don't do mosh pits, and crowds. Standing in the back oftentimes gets you an awesome view too (you can look over people's heads while sitting on barstools). I can hear the band great, I can see them even better, and all is well.
My boyfriend is extremely social so we (more like he) tend to make new friends at shows too... you might want to see if Katatonia has a forum or anything, and if anyone on the forum is going to the same show as you are. I did that when boyfriend and I went to see Epica, I had some friends from another forum I am on who were also going and we ended up meeting up with them briefly after the show. Just an idea. I know alot of people are wary of meeting people from the internet, but I don't usually worry when it's in a public place (ie, the concert).
I hope you get to go and have a good time. Concerts are pretty awesome.... I can't wait till I get to go to my next show.
_________________
Ari Levanah