Where does the toughness bonus as a warrior come from

Left-clicking on the ground is the most reliable way to deselect all targets.

ESC deselects any selected targets, but if nothing is selected you will bring up your menu (can be annoying mid-combat).

There is also a key binding to target the nearest ally, which will select yourself if no other allies are around. This is useful if you are having trouble finding a patch of ground to click on. This key is not assigned by default, so look for "Nearest Ally" under Targeting in Options->Controls.

You can also select the next closest target using TAB, in case you do actually want to direct your spells towards a different enemy then the one you current have selected. Then again, a left-click on the target works more reliably if multiple targets are in view.

There is also a Guild Wars 2 printable keyboard layout to help you visualize the default key bindings.

I also noticed this myself before. It does not show up on the amount you get from an event in the popup menu, however you do get the correct increase in your inventory karma amount.

More people verifying it here