Decide what you stand for before the party, not in the middle of it. Pressure makes terrible decisions.

Your judgment in a charged moment is not the same judgment you have on a calm afternoon. Pressure narrows what you can see, speeds everything up and makes the cost of standing out feel much larger than it is, which is a poor set of conditions for working out what you believe. Deciding early means the hard part is already done when it counts.

Before you go, settle the two or three things you are not doing and what you will say. Settle how you leave as well, since having an exit ready is what makes the line easy to hold.