Removable braces get loose with time as they are clipped in and out every day. For this reason, you should try not to fiddle with your brace. Also, avoid clicking the brace in and out of your mouth with your tongue. Always remove the brace as you have been shown, using two hands.
Even a loose brace can be worn reasonably well once you are use to it being in your mouth. Therefore, if you are able to, you should continue to wear it.
If you have clear braces, you can try to move on to the next aligner/positioner in the sequence. Contact the practice if you are unsure.
If you feel your brace is excessively loose and cannot be worn, contact the practice for an earlier appointment.