I often cook in bulk and then eat leftovers for several days. One area where I've struggled with this strategy is stir-fries. It seems that even if I get a well-thickened, flavorful sauce the day that I cook it, the sauce will go thin, watery, and weak-flavored as leftovers.
What I think is happening is that the salt and/or sugar in the sauce is putting osmotic pressure on the water in the vegetables. Since the sauce is added shortly before serving, the whole dish doesn't have time to come to equilibrium the day of. However, overnight, water leeches out of the vegetables and dilutes the sauce.
The same problem doesn't seem to happen with Chinese take-out leftovers, so I think it must be possible to avoid it. Does anyone have a suggestion?