In my case, I think my fissure could have been prevented.

I got constipated from eating very poorly. I never ate vegetables or fruit, couldn't remember drinking water for years. I basically lived off of junk food and diet sodas for years. I remember actually waking up and craving green beans one night. Looking back, I think my body was trying to tell me something.
I never really had any serious bum problems before my fissure. I had mild hems during my pregnancy's but nothing serious.
The best advice I would give for anyone wanting to prevent a fissure is eat your fiber and drink plenty of water.... Lol