Kind of a mix. It depends mostly on the experience level of the players. If they are highly experienced, they're in charge of their own stuff, including their dwindling resources. If they overextend themselves, oh well.
But if the players are relatively inexperienced, I'll give them reminders that they may be low on healing resources, food, etc. It's still up to them to adjust to that information and back off to rest and resupply or take the risk and press on. I'll react to their decisions and actions based on the situation they're in, regardless.