That depends on your version. In the latest beta, your best choice is to put as many candles, redstone inlays, stabilizers, skulls etc symmetrically around your altar as possible.
In older betas, craft as many stabilizers as you can, and place them pointing at the matrix.
Power them with any source of RF power (like vis generators, tho they will eat up a lot of vis, other mods RF sources are safer)
"how to lower mind?"
Im going to interpret that as either "how to aquire warp" or "how to get rid of warp"
how to aquire: eat lots of zombie brains
how to get rid of: either wait for the effects to wear off, or if you really want to rid yourself of temp warp, research the arcane spa and sanitizing soap
This depends again on your version.
I'd advice to read the thaumonomicon entries on those subjects, if youre unsure how they work. Most things are explained well enough.
Good day , I have a question , thaumcraft 6 -