You are absolutely right; small changes that become second nature are a great way to go about it. I often find that people start training with me and have the grandiose idea that they will now also exercise every day on their own (or eat no more junk food …. you name it). I try to tone it down by saying something like: “That is a fabulous idea, and it would be a wonderful end result. If you can manage it: great. What I would like for you initially to do on a daily (weekly) basis is ………” I then suggest a goal that seems realistically achievable.
Then, when they express frustration, you can get back with a diplomatic version of ‘I told you so’ but are also able to point to the progress made against the goals that you suggested.
This keeps the conversation on a positive note.
I wish you good luck.