Be predictable in the qualities that matter.

Unpredictability is fine in taste and dangerous in character. People need to know which version of you they are dealing with in the areas that matter: honesty, fairness, whether you will do what you said. Variation there means nobody can rely on any single interaction.

Decide which two or three qualities you want to be completely consistent in. Then hold them even on bad days. Predictability there is what allows you to be interesting everywhere else.