Welcome to MT hawkryger.
Some really good suggestions above thread. If I might add a couple for you to think about and maybe try? Disclaimer, I do not practice CMA.
Sometimes a persons perspective just needs a bit of opening up. The fact that a person moves the way that they do says something to them if they will listen. It is obvious that a person moves in whichever way because that way has in the past worked for them. It has been successful in someway that helped the body recognize it as a proper and correct way of moving. Recognizing that since the current way of moving has worked for them in the past is proof that it is not wrong, it is merely different. It is easy to get worked up by listening to that inner complaining/blaming voice, which by listening to it often just causes an increase or greater likely hood in the less desired outcome. In the case of the OP, an increase of excess tension. When hearing that blaming, finding fault inner voice, give yourself a pat on the back for having the sensitivity to recognize that you are moving with excess tension and let out that breath that was suspended, lol. Tell yourself that it is not wrong, just different, and right now you wish to try a different way of moving. Chuckle at yourself and look around - perhaps there are plenty of people training right beside you that are more than willing to give you lumps, no sense in giving yourself lumps.
One of the ways to move in a more relaxed manner is to first add excess tension. It is funny but for me true - trying to relax specific muscle groups can be difficult simply because your body does not yet have the specific neural pathways that would allow the muscles to release the held tension, or as often is the case, the nervous system is firing out of a fear response. Doesn't really matter. Either way you can trick the body into relaxing a bit. You will not be as free as your sifu or instructor, but you will be freer. Simply do which ever movement you were doing when you noticed the excess tension but this time make your body as tense as possible, head to toe, while still being able to move. Think isometrics. The body can be tense extended or compacted, heck do it both ways or mix it up. Then do the movement as relaxed as possible, think floppy and not martially. It doesn't have to make sense martially. You want to explore both extremes, too much tension, not enough tension. Right after, go back into the movement and try to move natural which should be somewhere between the two extremes and keep breathing.
Another trick is to focus your mind on something other than what your body is doing/feeling. Do the movements but focus entirely on breathing for example. Or focus on the second/minute hand on a wall clock, can you get thru a series of movements and never lose sight and consciousness of the ticking clock?
Good luck
Regards
Brian King