Depends on what you ate mate. I've experienced this too.

One, it could be that what you ate interfered with your body's mercury elimination to a degree where you were no longer getting symptoms. Sugar and milk can do this.

Two, certain foods can significantly affect your biochemistry. Sugar can give you a kind of high, and anything like it which causes an insulin surge can also cause your body to convert a lot of tryptophan into serotonin. Plus, sugar affects your opiate receptors, and it stimulates endorphin production. It also raises cortisol, which could feel like a relief to you if you have adrenal exhaustion.

What a sweet deceiver sugar is. I keep falling into this trap myself. Sometimes the short-term relief is nice, when it comes (it doesn't always). Unfortunately there are always consequences to face.

Would you like to tell us what you ate, mostly, and how it was different from the way you normally eat? Maybe you've actually been starving your body of a certain nutrient it needs and it was telling you big-time.