"Bum in the clouds. Face on the floor" is one rather exaggerated description of the sort of position aggressive frame geometry throws your body into.
Aggressive geometry bikes have short headtubes and steep frame angles. The former put the rider into a more aerodynamic position (lower head and flatter back) whilst the latter create a shorter wheelbase resulting in snappier handling.
These types of bikes are designed more for competitive racing than long distance comfort.