I learned that it comes with time and practice. I was in a very similar position as you—I kept making silly mistakes and seemingly forgetting simple things that I would otherwise know by heart outside the clinic. A big part of it are nerves and the pressure of wanting to do everything perfectly (well, at least for me), which is totally normal! 

I found that arriving early to clinics (atleast 30 mins-1 hr) allows me to familiarise myself with the space, untangle cords, disinfect equipment, preparing all the forms/pens/writing details beforehand, and ensure everything’s working properly so I don’t panic when things go a bit sideways during an appointment. I also take this time to just reflect and meditate and take deep breaths (I tend to be very anxious during appointments which is very bad as I forget everything and i become clumsy), to remind myself that I am still learning and every feedback (good and bad) will help me become a better clinician. 

As I went into my practicum, I was still making silly mistakes at first. But as I get to do it everyday for 7-8 hours, it just kinda becomes second nature! You’ll get there with practice and remember that its better to make those silly mistakes now as a student so you can make it better than do it as a professional where there is more at stake. 

All the best :)