Here's some advice on all 3, and I don't even ask you to buy my supplements :)

1. Practicing a healthy diet is self-love

2. A daily treat is not what breaks your diet. Have _a piece_ of chocolate, sweets or snacks now and then. If you (still) lack the self-control to not eat the whole package, help yourself out by repackaging in daily-compatible portions. Meaning is not gained by consuming anyway.

3. Taste preferences are in big parts a matter of habit. Also prepping doesn't necessitate you eat the same thing for a week. You can freeze a lot of things for longer and thaw them in a mixed manner.

Imo the issue is that people seem to lack a combination of knowledge, time to prep or motivation. Lack of knowledge could be solved with information campaigns, lack of time/motivation is a consequence of people having to spend so much of their time doing a dayjob just to get by, embedded in a culture that puts no value on thriving humans.