i usually have a bottle of wine open and have a glass most evenings. the bottle can sit there for 3 or 4 days, depending on how much and how often i've had some. it still tastes the same to me although i'm sure a wine buff would throw it out. if it tastes ok to you, then drink it.
fizz keeps it's fizz for a couple of days, it's not like lemonade which goes flat much quicker.
incidentally, i don't think it makes any difference whether it has a stopper on or not once it's opened.