There are something like 80 more Democrats in the House right now than Republicans, losing one seat doesn't make any difference.
The Senate is a whole other story with the Republicans trying to filibuster every piece of legislation, Democrats need to get to 62 or 63 Senators to get stuff passed. We can't afford to lose any seats in the Senate.
What if Democrats lose control of the House in trying to get those 62 or 63 seats in the Senate? If Democrats lose the House, it probably isnt coming back. If they lose a Senate seat, they will likely get it back.