The best thing to focus on is the pace you are moving at and the precision of your track rather than the control over the jump itself. It’s good to remember that it’s your horse and not you who is doing the jumping so concentrate on setting up the fences as best you can to give your horse a chance to put in his best effort.
At home, make sure to always practice precision, whether in flat work, poles, or 1,40m fences. This will greatly help in control in the shows. Best wishes on your training!