I turned on an ability and the icon changed into a blue and white circle

There are some groups of special abilities that do not expire on their own and are mutually exclusive (a character cannot have more than one ability out of the group active at one time). Examples include hunter aspects and paladin auras. Once one of these abilities has been activated, clicking the button for it again will turn it off. This is in contrast to most spells, which can be cast again while active in order to renew the duration. To remind you of this, the icon changes into a blue and white burst while it is active. Clicking this icon dismisses the effect.