If push came to shove I could probably take vacation even if my manager didn't think it was a good time, citing mental health/family issues/whatever. But that would involve spending the same amount of goodwill as declaring "I've already earned this PTO so I'm using it whether you want me to or not", and I would be hesitant to do either of those if I had even the slightest bit of respect for my company or co-workers. And if I didn't have that respect for the job, why would I be working there in the first place?