An independent observer agrees...when a beautiful twenty-something girl from [redacted European Community nation] is practically throwing herself at you at a [redacted December/January holiday] party, one should avail themselves of the opportunity and close the deal, because it might not happen again. Ever.
Even if one has been told repeatedly "she has a boyfriend." (Apparently not an issue at that particular moment in time.)
Even if she's a friend's sister and it could get a little awkward later on. (A. You know, it is possible to overthink these things. B. We're all adults here. C. Anything is preferable to mercilessly beating oneself up afterwards.)
Other relevant sayings:
* It's better to ask forgiveness, than permission.
* Man up, nancy.
* A-B-C. A-Always. B-Be. C-Closing. Always be closing, always be closing.