It's not a matter of "not like it". If you fail in Ukraine there are other parts of Russia that would like to leave and would be emboldened by seeing you couldn't take Ukraine. The threat of retaliation would be shown hollow.
Yeah, and? Do you realize that you just gave away the whole pan?
Same logic applies to virtually every country, Union, etc. You think no one in Texas wants to leave US?
Having said that, Unlike US In, Russia there are not that many regions which want to leave.
And these who want to leave (caucuses) are more than welcome to do so as far as I am concerned. Don't care. I know they will turn into shit immediately without Russia. Chechnya tried that. Still there are some external forces in the west which try to make it happen for the reason of creating problems for Russia.