What's really important is not letting what happened in 2010 happen again in 2022.
Democrats have to hold the House, and the decreased majority gives far less room for failure there. Having Governors in states like Wisconsin and Michigan will help, but there will likely be a seat lost in Maryland to Hogan's veto over a 7-1 map as currently exists, and Arizona Republicans will probably try to draw a map that won't sometimes result in a 5-4 Democratic majority, etc.
As for the Senate, Mark Kelly still has to win again in Arizona, while Michael Bennet, Catherine Cortez Masto, and Maggie Hassan are all up for re-election in close states. Meanwhile some of Marco Rubio, Richard Burr, Pat Toomey and Ron Johnson need to be knocked off, plus Kelly Loeffler if she wins in Georgia (otherwise, Raphael Warnock's seat will need defending).
Given the historical performance of the President's party in midterm elections, this could be a very tall order.