One thing you might look at are your tires. Do you have the right ones for your terrain? Are they knobby enough, grippy enough? And what about tire pressure? If you are a road rider you probably pump those tires up to maximum pressure, right? Well your mtb tires may say "to 65 lbs" but you really only want to be running around 35#. This will eat up a lot of bumps and help keep you from bouncing around and in contact with the ground, hence less crashing.

Riding alone is not a good idea.