I don't remember the last time I bought a soda. The last time I had any was a couple weeks ago when I got a cup of ginger ale on a flight. Before that, I might have bought one in March at a hotel? I vaguely remember getting a soda. I read somewhere, probably Reddit, that discipline is stronger than motivation. Motivations can change, but having the discipline to do or not do something is more firm. I'm going running after work today. Why? Because it's Monday and Monday is a run day. It's overcast and a little cold and there's some scattered rain. I'm not motivated to run today, but my discipline doesn't ask if I want to run. Barring an injury or dangerous weather, I'll run. That's my suggestion for you to consider. It may be easier to be a person that doesn't drink soda than it is to be a person who doesn't want to drink soda.
Still, here's a little motivation your way: This year, I started running when it was minus 20 degrees centigrade. Overcast, cold, raining? That's just my kind of a vibe. :) Elaborate?It may be easier to be a person that doesn't drink soda than it is to be a person who doesn't want to drink soda.
For me, discipline is deciding once to be the type of person who runs three or four times a week. Motivation, for me, is deciding if today is a day I'm going to run. It's too easy for me to say no, not today, I'll run tomorrow instead. At times I don't want to run, but how I feel that day doesn't matter. I've decided I'm a runner, and my lack of motivation that day doesn't matter. I'm still going to run. Maybe that's a really narrow difference and doesn't work for you. We're all different, and what works for me may not change anything for you.