My sister gets seizures a lot. The doctors did all kinds of tests and have no idea what causes it. They won't put her on meds either cuz sometimes she'll go for over a year without one. They're just random.
But what I do know is when she smokes weed, the risk of her having a seizure greatly increases. At least twice right after smoking she had a seizure. I haven't seen or talked to her in months and her bf smokes weed, so it could have happened again. I know she doesn't (or didn't) smoke it a lot. Only once in a great while, if other people offered it to her.
So just watch yourself. I'm not saying to stop smoking or anything, especially seeing as you have only had one seizure, but if you start having them right after smoking, or the same day you smoked, you should think about cutting back.
Oh, and when she's really really stressed, she has a seizure. And when she sees her own blood, like if she gets cut or something and blood just pours out and won't stop. One time she got a tiny little nick on her hand, but the blood wasn't stopping, so I wrapped it in a washcloth and had her sit down on the toilet and hold her hand over her head. Unfortunately, I wasn't thinking to keep an eye on her face or I would have noticed the warning signs (pale, eyes rolling or difficulty keeping them open). Just when I was about to tell her the bleeding stopped, she slumps over. I caught her just before she smacked her head, but she's shaking like crazy, weighs more than me already, totally deadweight, and on top of that, she happened to be wearing a slippery silk shirt. It was very difficult to keep her from smacking her head on the sink. I jokingly yelled at it for all that stuff when she finally came around, in attempt to cheer her up.
So maybe keep a journal and write down everything that happened the day you have a seizure, and maybe you can figure out what causes them for you. Have people who were around you that day help you, in case you can't remember what happened. My sister often forgets what happened before the seizure. We usually have to fill her in.