Nothing is more satisfying that
ex post facto Russian whining about their latest foreign policy disaster.
1) Russia applies pressure to Ukraine not to sign the association agreement with the EU.
Q: Why? The treaty was not exclusive and wasn't harming Russian economic or trade interests in Ukraine.
A: Because Kremlin does not want a strong, economically successful AND democratic Ukraine that looks to the West instead of obediently waiting for instructions from Moscow. More generally, European Ukraine on the border with Russia would send a clear signal to the Russian opposition that it's time to end Putinism and follow suit. Economic interests are secondary, this is a matter of long term survival for the Russian autocratic regime - Ukraine is too big and too similar to Russia, i.e. potentially too dangerous as an example that there IS an alternative to Putin's post-soviet autocracy.
2) Russia urges Yanukovych and his government to use force against peaceful protesters. As a result, the crisis escalates into violence, then more violence, and eventually massacres in the streets.
3) The regime falls apart, Yanukovych is deposed, and Russia is looking for ways how to further destabilize the new regime, whilst toying with the idea of annexing the Russian-majority provinces.
4) Russia whines about being treated unfairly.
...
My advice: grow the eff up.