Keep in mind that for many of us, including sciency types like me, just beliving something causes side effects can cause real measurable symptoms.

I had really annoying side effects from medication until at one point I realized I got the same side effects almost like clockwork even when I had forgotten to take it. At that point the side effects just disappeared completely I haven't seen them since.

(That said, the effect you felt might be real or not but I still agree with you that cutting back on sugar is smart.)