We already know a Clinton with a Republican congress is a pretty terrible combination, so it's not like having Hillary win would be that great. If she loses, the Democratic party can get some new leadership that actually wants to build the party, and the 2018 and 2020 elections will be important for congressional and state legislature redistricting.
If you think Clinton with a Republican congress (the senate isn't certain, btw) would be bad, try Rubio, Cruz, or (God forbid) Carson or Trump with a Republican congress. Also, if Democrats squander their opportunity to take back the senate in 2016, and end up with 47 seats or less, the senate probably stays Republican until 2022. Unless 2018 is a bigger wave year than 2008, Democrats won't get the house, either, so Republicans will get at least four years of complete control. GIVING UP ON 2016 IS A HORRIBLE IDEA!