Try drinking a sparkling mineral water such as perrier or similar. Since diet soda is your thing maybe it isn't the flavor your crazy about, but that refreshment the carbonation gives you. I heard aspartame isn't healthy. Overall, if you can't cut it out of your diet I wouldn't freak out. Most importantly, your being more aware of everything else that goes into your body.
There will always be somebody somewhere who says something is bad for you. Great. Wonderful. We'll just eat nothing, get to our goal weights and die anyway. No one is going to tell me what's good or bad for me except for me because I am the only one who has to live with the consequences of my choices. Don't forget there was a time when doctors recommended against exercise for women because it would damage the uterus. No one really knows what is going to happen so if you like diet soda and it makes you happy and keeps you from making a poor choice later on then chug-a-lug. If you don't want it then don't drink it. No one is forcing it on you. But for the love of grits and gravy can we please just all agree to disagree and get on with our lives?