I wasn't addicted to diet soda, but I was addicted to Mountain Dew for most of my life. If you saw me, I had a Mountain Dew in my hand at all times. There would be days that Dew was all I would drink, and occasionally I would get tired of soda and have Sweet Tea.
My first attempt to break the soda addiction, I went to Root Beer and Cream Soda instead of Mountain Dew. But the sugar content was much higher in Root Beer. That attempt failed. More recently I just put the soda down all together and would drink Arizona Southern Style Sweet Tea, but that didn't last long. I then went to drinking water, and lots of it. Water not having any flavor was not quite doing it for me, so I started adding lemon to the water. Now, I don't miss the soda.
I ran out of bottled water at home the other day, and did drink a small amount of Coke, and I thought it was going to kill me. I won't make that mistake again. The flavor was good, but oh the heartburn it caused.