Cracking knuckles, is it healthy?

I have been cracking knuckles for many many years, and it has not affected me one bit. It is not just my fingers; I am able to crack arms, toes, ankles, knee joints, and my neck. I crack them and it feels relieving (maybe that is why I do it on a daily basis) , however people that I know have said that it harms my joints and soon they will deteriorate all together. I do not know if this is true.