Fixation is a natural part of the way we train new techniques and new forms. When you practice, you say, "Okay, I'm going to work on XYZ kata." or "I'm going to train ABC technique now." We then proceed to drill the technique repeatedly.
This is good training at a very low level, but it's something that needs to be abandoned at a point. In my estimation, this is the point where the student begins dissolving techniques into the handful of principles at the core of any art.
In the Bujinkan, if I examine the torite kihon goho (5 basic techniques in our art), I'm looking at five techniques that deal with locking the body by means of the joints, disrupting the balance, creating exceeding pain, and controlling the opponent.
Now, rather than saying, "I'm going to practice ura gyaku" which gives me two techniques to practice (right and left), I'll instead say, "I'm going to practice disrupting balance." Now if I only know the torite kihon goho, I am practicing 10 techniques (5 techniques, right and left). But these techniques are composed of small pieces, so I skip portions, change movement, and seek to still disrupt balance. Now I'm no longer practicing techniques but principles, and I'm not rooted to any one.
So then I'll work under stress; rapid-fire randori after a few laps around the room to elevate my heart rate. Don't think, but respond and let the attackers attack how they will.
When you stop focusing on performing the technique and begin to just move, you'll find 1.) that you know the techniques you've been training and 2.) that you do not need the techniques to be effective.