Almost a half of my life I have been living in a society, where my nation was forced to assimilate. For 40 years communistic Russia tried its rusification policy on Latvians by bringing in workforce from different parts of USSR, by issuing laws that all documentation has to be in Russian, prohibiting the practise of Latvian folk traditions with only few exceptions.
How did we feel? Angry, oppressed, spiteful, distrustful, distant, hypocrite in front of officials.
The result? We did not assimilate at all, we practised our traditions in secret, we cherished our language and identity and made a use of it when there was appropriate moment to become independent again.
Now we are a free country with a large Russian population (one third), once having been the victims of forced assimilation ourselves, we try to integrate them rather than assimilate. Even then Russians react with anger, rebellion, causing never-ending conflicts.
This is why I think that no-one is completely comfortable with having to integrate, and even more negative feelings are provoked by assimilation. Even if assimilation is not forced upon a nation and is merely natural, one feels sadness and deprivation.