I've also suffered from anal fissure for more than 5 years.
This was the most terrible pain in my live. notably the first year. The last year i found that applying pure olive oil inside anus before and after defecating, relieves pain and cures the fissure very quickly. I thing the Olive-Oil have wonderful healing properties. Also drinking a high quantity of water (and lot of fibers) is the key to have a smooth bowel movement. In hot season i drink about 5 liter of water per day , and in winter about 2-3 liter per day. I also drink 2 glasses of water as soon as I wake up from sleep. This make my to defecate every morning.