It's kind of a paradox: having free will depends on whether or not you believe you have it. According to a recent study published in Psychological Science, when you deny the existence of free will you're actually hindering your brain's ability to perform voluntary action.
Here's how the study worked, according to Wired Science:
30 people [were asked]to read passages from Francis Crick's 1994 book The Astonishing Hypothesis: The Scientific Search for the Soul. Half read a passage that didn't mention free will, while the others read a passage describing it as illusory. All were hooked to electroencephalograph machines that monitored electric activity known as "readiness potential," which is linked to the neurological computations that occur in the milliseconds before voluntary movement. The test subjects were then asked to press a mouse button when a cursor flashed on a computer screen for several seconds. Those who read the passage dismissing free will displayed significantly lower readiness potentials. Their actions seemed to involved less voluntary control than the control group's.
It seems free will has a bit in common with Tinkerbell, as it's more likely to exist if you believe in it. If you're feeling like you're not in control of your actions, it may be worth reaffirming your belief in voluntary action. Maybe it'll make the difference.
Disbelieving Free Will Makes Brain Less Free [Wired Science]