In my 4.0 world it's: 1.Impatient/Trying to end point 2. Trying to do go too big (not the same as 1) 3. Trying to hit "the best first serve possible" 4. Folding mentally while down 5. Not attacking opponent weakness.
8:02 One more point: as Nadal sends a message by pumping his fists after a winning shot, so do many people (myself included) send the opposite message by letting their heads hang low once they missed a ball. That just looks terrible and gives your opponent LOTS of confidence. It's hard though staying in emotional control the longer the match goes on. So what I think helps is running every day and/or using the exercise bike, just to build up stamina. So then you can still be running after 1h and be upbeat on the court.
5:10 I find that video analysis also helps. My forehand approach shots can be hit or miss, and I couldn't figure out why. So I looked at myself on video: it turns out I am not rotating my torso - likely because my mind is already on the way to the net and as a result, my body forgets to rotate. Of course, then the control over my shot is very shaky. So the solution is to focus on hitting the ball, not moving forward (yet).
