Don't panic. Based on history the party that has the White House almost always lose seats and many times lose power in either the House, Senate, or both.
But here are the facts of the matter. Since Republicans still control the Senate, Trump will be able to appoint federal judges and if a Supreme Court pick comes up he will get that approved too. He will also be able to get approval for any treatises or trade deals.
With the Democrats controlling the House I do see the House and Senate being able to work out a deal for an infrastructure bill. Democrats love to spend money, so a spending bill is something they might go for even with Trump as president. They won't be able to raise taxes, give amnesty to illegal immigrants, or really get much else done. Trump will also not be able to get the wall or repeal Obamacare, but these will be issues he can use in 2020. Democrats will have many ongoing investigations into the Trump administration and might try to impeach Trump. But without the support of the Senate they can't remove Trump from office.
Trump will still be able to use Executive Orders to get some things done and he can use the executive branch and its different departments to cut regulations which will help businesses and the American people.
I see us mostly having a government for the next two years that gets very little done and we may even get a government shutdown or two. That can be a good thing as the less the government does the better it usually is for the country. Most of Obama's successes were because he had a Republican Congress that didn't let him pass bad bills that hurt the country.
While this election wasn't great for Republicans or Trump, it could've been worse. Now we just have to be ready for 2020 and reelect Trump and take back the House.