My son tells me that every time they think we have a "usually" in place I change it.  I'm kind of like that:)  As in we "usually" order pizza on Tuesday evenings.  Lots of pressure to order pizza then, when sometimes I'd prefer to cook, or laze at the pool...just an example.
As far as should's.  I catch myself thinking "should" quite frequently.  Then I think "should" according to whom/what standards.  Others?  Then perhaps I shouldn't :)