How can I stop drinking diet coke at lunch I drink it every day I can't stop my self?

Diet Coke. I believe you are referring to "diet coke" not just any diet cola. In that case, i believe that overdoing sodas with asparatame--nutrasweet is potentially damaging to your healththe breakdown product of nutrasweet is formic acic--or formaldehyde-same stuff we preserve dead bodies with! it is not good for you. Switch to a diet cola made with stevia. Second best splenda. Then wean yourself to h2o.
Try pepsi. Try pepsi then.