Not least amongst those things is our food supply from Europe.
You must have noticed just how much wonderful food we import from Europe?
Not everybody wants to travel or work in Europe of course, but some do.
My European citizenship is very very important to me personally. I will not have it taken away without a fight.
My views about legislation have been posted before but generally I have found/perceived that the EU is more ecologically minded and progressive than the UK Govts.
If a country is not united in its direction, then a reasonable and democratic way to resolve the issue is to have a free public debate and then a vote.
If the vote goes against you there isnt really any point in repeating the arguments that you made before the vote and which were not accepted as a deciding issue by the majority.
It may be factual that the people who voted leave were any of the accusations pointed against them, xenophobic, stupid, racist, uneducated, gullible, fascist, little Englanders and just plain wrong. but in a democracy EVERYBODY has an equal vote. You can not expel them from the electoral booth as easily as you can remove their platform, "shadow" them in Google, close their Twitter accounts etc.
This "weakness" of democracy is also its fundamental strength.