I am no expert but after two years on the medication your brain chemistry has changed to live with the daily dose of that drug.
I hope you fully understand that.All the neurons and synapses.

When you reduce the medication your body/brain will have to try to make itself "normal" again. This might be detectable or might not be.Don't blame some bad luck on the lowering of it.
You will have the usual good days and bad days of life, but the bad day might be worse than normal. Try to tough it out if you can, otherwise you will undoubtedly go back to the usual dosage.

Bad news is that your brain chemistry might be irreversibly changed(after two years) to expect a daily dosage of that drug

someone said you might have thoughts of suicide on withdrawl.
Lots of people(normal and crazy) have those thoughts, the important thing is to remember your own morals and values.