A shank is hitting off the hosel.

A quick fix for hitting off the hosel is simply setting up with the ball lined up with the toe of the club.

If you are hitting the ball with the clubface wide open, it is a different problem.

Hey Tim, I believe it is both physical and mental. Here are some anti-shank things you could work on.

Try choking down on the grip a little bit.

keep your weight more on the heels of your feet.

You could also try putting a towel or a headcover  under both arms and make a swing without them falling down.

Last, try not to think about it too much.

Hope this helps!

Connor,

TIm, the truth of the matter is, shanks are caused from the ball coming off of the hozel of the club. What causes it can be many factors, none of us on here can accurately tell you what that you are doing wrong, because we can not look at your swing to determine path/face ratio. The best advice I can give you is to go see your local course pro. He/she will be able to fix you up in a matter of minutes! Hope this helps!

If you've been "practicing" alot recently then the cause could just be fatigue.  As hard as it might be, sometimes the best cure for the shanks is to put the clubs away for several days, and instead of living/breathing/thinking golf, just enjoy everything else life has to offer.  After several days the problem might just go away.  If not, then it could be a number of reasons as others have mentioned, it could be that you're taking it too far to the inside in the backswing, coming in over the top, setting up too close to the ball, etc. etc. but if it persists, then it's time to see your local pro.

I've experienced all of this before.

1.  In 2008, shanks would pop up after 45 min on the practice greens or the driving range.  The only way to fix them was to stop.  Taking a more compact backswing appeared to minimize it.  The main thing in fatigue is the lower body locks up.

2.  Loss of balance.   If you are sometimes too far from the ball and too upright, you fall forward and the hosel catches.  Or it APPEARS to be a shank because it is a toe down hit that causes the ball to shoot 45* right.

3.  Taking it too far to the inside for me is more of the cause of snap hooks because of weight shift. 

4.  Standing too close to the ball is about 99 percent of the swing faults.  Over the top causes a pull and trying to use an inside out swing causes a push fade or a shank.  The main place where I had this recently is hitting from a ball above the feet lie....   you have to choke down a bit and stand further from the ball and also have to aim right of target because it will go left (for righties).

5.  Not clearing the hips on the downswing causes both severe pulls and shanks.

I have a problem with shanking, and to compensate for it, I've just moved further from the ball, and now I hit it off the center.