If you take your retainer out for a week then your teeth will usually move out of position.
Then when you place the retainer back in your mouth on your teeth it will usually feel tighter than it was before removing it because your teeth moved.
You need to continue wearing your retainer until the dentist says you can quit wearing the retainer because if you remove the retainer too soon then it defeats the purpose of wearing the retainer in the first place.
Then your teeth get misaligned and it's like you never wore the retainer in the first place.
So always wear your retainer until no longer needed otherwise your teeth will get out of position.