It's not worth dying for NATO membership or an ukrainian Crimea. And nobody should be forced to fight in any war.
It is about cost/benefit.
If Ukraine would tell: We are looking for a compromise (no NATO membership, Crimea belongs to Russia, ...), I could change my mind and support them.
If Russia would invade another country there's a new cost/benefit ratio.
And I think Russia will not invade any western country. I live in Germany and I'm not scared of Russia. They (Soviet Union actually) left East Germany peacefully.