Kevin Drum provides one:
Liberals, you should rein in the triumphalism. Obama won a narrow 51-49 percent victory and the composition of Congress changed only slightly. This was not a historic vindication of liberalism, and it doesn't mean that we can suddenly decide that demography will sweep us to victory for the next couple of decades. The plain truth is that although an increasing number of voters are turned off by what Republicans represent, that doesn't mean they've become lefty converts. A lot of them are still pretty nervous about a big part of our agenda, and we have a lot of work ahead to get them more solidly on our side.
Also: No matter how much you hate to hear it, long-term deficit reduction and entitlement reform really are pretty important. Just because conservatives abuse the point doesn't mean there isn't something to it.