Unsolvable whack a mole

I see the Earth as a whack a mole game from hell. One Issue is fixed and then it is replaced by 2 more problems. The world we live in is a never ending cycle of unsolvable puzzles. 

One puzzle that is evident now is Brexit. The island of Ireland is two states. The Republic of Ireland and  the "United Kingdom of Britain" Northern Ireland. The British part of Ireland is being dragged away from the EU with the Rest of Britain but the Peace agreement that stopped the conflicts in Ireland involved having a soft border between the two states. But if we are separate from the EU, we need a hard border because we will change our own import tariffs and the member states don't want untaxed goods from countries with low inflation competing with their own products. The EU common market is very important to many EU states. 

So how do you solve a problem like NI Brexit? We want to have some kind of trade deal with the EU but the Northern Ireland border has to remain soft. Low friction and free movement between the two states.