Personal anecdote indicates that "work hard" and "do your best" have slight negative correlation to a positive observed outcome in some workplaces.

Minor titration efforts suggest that "appear to work at slightly above the observed median level of effort" and "if doing your best and following orders conflict, follow the orders" work better in practice. This strategy has yielded more positive performance reviews than opening up full throttle. It depends a lot on workplace culture.

Save your best efforts for personal projects, or for a company of which you own at least a whole 1%.

Companies in this decade generally do not reward competence or diligence, or respect vocational passion. If your specific company does, then by all means, give them your best. Otherwise, don't cast your pearls before swine.

Definitely be kind and pursue many opportunities.