Positive charges "move" from higher to lower potential It's my understanding that whenever an object gains or loses electric charge this actually corresponds to losing/gaining electrons (protons do not move). So how can a positive charge always move from higher to lower potential?
 A: 
It's my understanding that whenever an object gains or loses electric charge this actually corresponds to losing/gaining electrons (protons do not move).

This is not always the case.  If you're talking about everyday static electricity (getting zapped by a door, for instance), then yes, electrons are transferred.  However, more generally, ions (e.g., protons) may be move and carry charge with them.  For instance, in a lithium-ion battery, lithium ions are moving due to a potential internal to the battery.

So how can a positive charge always move from higher to lower potential? 

Positive charges always move from high potentials to lower potentials.  Negative charges move in the opposite direction.  The dominant charge carrier (species) that moves depends on the situation at hand.  
In many situations, the ion cannot move freely due to, for example, bonds with other ions.  Electrons in the valence band of insulators are more readily "stripped" off the atom and can become free charge carriers.  Electrons in the conduction band of metals and semiconductors are also able to move more readily within the material lattice.
A: Positive charges move downhill because of convention.  It is to stay in line with other potential theories, particularly gravity, where the "charge" is mass, which moves downwards in the gravitational potential field defined by $\phi(r) = - \frac{GM}{|r|}$.  In an electronic system, however, positive charges are fixed in their position within a component (e.g., a wire), so instead the mobile, negative charges, electrons, move uphill.  
The result is the same tendency of a system to move towards its lowest potential state, it's just that the charges are mixed up.  You can thank Mister Benjamin Franklin for that one. 
