You see... That's about country prestige. We had enough time to demonstrate our peaceful intentions and restraint to the world. Now Ukraine is a country that has thousands of armed terrorist on it's territory and does nothing. It doesn't protects basic right of it's citizens in Crimea.
Now it's time to declare state of emergence in Crimea, commandant hour and everything that comes with it - anyone coming close to a military base=Shoot anyone armed on the streets=shoot. If this means a war, then it is war. Else... There are no country and few months later Russians will just go and take the whole country.
That's stupid, you don't play to the enemies strengths, you play to your strengths.
Russia's strength is raw military power. They have a bigger military and everyone knows it. Ukraine's strength is that it has western sympathy. The west is hesitant to get militarily involved (unless Russia outright attacks western ukraine) but they are getting economically involved. Ukraine is getting a juicy economic stabilization package. Russia is getting sanctions.
The side that outlasts wins. Ukraine is getting stronger, NATO membership and it's security guarantee is now a much easier proposition and the west is willing to pour a lot of money into Ukraine if that's needed. You'd be stupid to not want this to be an economic showdown. Russia on the other hand is dependent on those same western nations for the import revenues that make their economy run. If western Europe decides this summer that it needs to start investing in alternative but secure natural gas sources (of which there are a lot, it's just an expensive proposition) then Russia's economy will be feeling the pain for decades.
In a war on soil close to home nationalist sentiments drive everything else aside and mothers send their sons to die while people accept economic hardship. All the soft power that Ukraine has, and it's a lot, will not matter because in war the weapons decide everything. But as long as the peace endures Ukraine has a very strong hand. Russia holds the ground but Ukraine has everything else.
My bet is that Ukraine wins this and Crimea will be part of Ukraine in ten years time because I think the Ukrainian leadership has been smart so far and will keep being smart while Putin has been stupid and has put himself in an untenable position.