Extension for office action

I recently received an office action for an application at the USPTO
with a deadline to respond within 3 months with possible extension to
6 months.  In consideration to other matters, I am wondering how
difficult or easy is it to get an extension for responding to an
office action.  If for any reason, your request for extension gets
denied, is it still possible to respond within the 3 month period?
Are there any adverse consequences for requesting an extension?

Thank you in advance ...