I am a believer that the yips usually start with some type of poor mechanics, be it bad aim or whatever. I think that causes some poor putts, then it creeps into your brain and things go haywire. That's just my opinion, I know Mangum and others disagree with me.
When I was in college, I was a great putter. Not the best, but really really good. Then I took 8 years off from the game, came back in 2009. Immediately I came back and started putting just like I did in college, but after awhile my putting soured and probably the worst putting I've had since I was 14 years old. Eventually I became a golfer that didn't 3-putt much, but didn't make much either...regardless of length of birdie putts.
Lately I've been putting really well. Getting closer and closer to my college days and my ballstriking is far better, thus lower scores (shot a 68-73-75-73 last 4 rounds on hard courses).
The thing that has worked for me is putting much more of my focus on speed. And I mean REALLY REALLY focus on the speed and stop worrying so much about aim and even green reading (it has been sweltering hot, so wasting a lot of time reading greens for a casual round isn't fun). I basically try to keep my speed so every putt reaches the cup and/or goes no further than 24" past the cup. Even if I make a pretty bad mis-read, if the speed is within that range I'm happy. Conversely, if I made a good read but go 3-feet past the cup I still consider that a 'bad putt.'
I think I just got to the point last year where I had a pretty aggressive speed with my putts and thought that if it went 3 to 4 feet by I had a 'that's good enough' attitude. Now it's a mega amount of focus on the speed.
The greatest putter I ever saw was a friend of mine that I used to travel to mini-tour events. Had the ugliest stroke you could ever see. And his putt speed was ultra aggressive. But his speed was remarkably consistent and I'd put him against anybody in a putting contest, hands down.
3JACK