Remainers. Show some humility and accept the decision made in June. Don’t snipe from the sidelines or try to cook up ways to reverse the decision (and don’t wait passive-aggressively for the whole thing to collapse). Like it or not, you’re going to need to help make Brexit work.
Leavers. Remember that Britain voted to leave the EU and nothing else. Don’t assume you have consent for more, don’t patronise Remainers and don’t dismiss their fears about the future. Accept that the final settlement must be a compromise and seek consensus.
For once it’s really meaningful to say that we’re all in this together.