Actually had such an experience the other day. I have all the morning-pills I have to take in little cups so that I don't think about choosing the right ones. They didn't seem to help me so far. But most of them are supposed to take effect after an extended time.

One time I absentmindedly took a cup in the evening as well. And I finally actually did feel some betterment the next morning. But because I took a handful of different pills at once I now have to find out which one actually did make a difference at doubled dosage. I could already eliminate one.