I had IBS-D from about the age of 10 to the age of 29. I'm 42 now. What changed for me 13 years ago is that I learned that humans require eating dietary fiber and changed my diet to accomplish that.
I eat about 40 grams of dietary fiber and drink at least a gallon of water every day. It actually takes work to reach this goal, but the plus side is that once I started doing this I have had no symptoms of IBS for the past 13 years.