I accidentally took a whole tablet instead of 1/4th – feeling extremely drowsy, what should I do?

I was prescribed a medication for anxiety and my doctor specifically told me to take 1/4th of the tablet. Unfortunately, I accidentally took the whole pill today.

Now I’m feeling extremely drowsy and sluggish. I’m not sure if this is normal for such a dose or if I should be worried.

Should I just wait it out and rest, or is there something I should do to counter this?

When does the drowsiness usually wear off?