Yeah, sometimes I mutter to myself in response to altitude changes with and grumbling “unable” ! 
I often don’t add an approach in the plan because I don’t know what runway to assign? So I select it manually during the flight in the on-board system.
I also begin my descent early using flight level change requests, and that helps. And other times, even when I’m self-managing my flight levels sensibly, when the ATC assigns my runway and approach, it asks me to climb back up to 14000 or so. In those cases I patiently ignore them and stick to the procedure I loaded, and eventually they give up when I get further into the procedure. Sometimes the tower sees sense when I contact them and assigns me to the correct altitude for the approach.
I always use the charts and fight plan, and stick to that. If the ATC had their way, we’d all be using our sick bags. 