Professional musicians do whatever is necessary to acquire the very best instruments they can find and then maintain them in flawless working condition. Singers are born with the only instrument they will ever own. It is therefore even more important for you to optimize and maintain your instruments as well as you possibly can.
Our practice of singing must to balance the sublime with the ridiculous.
While many disciplines can support your singing, meditation is the one I find most valuable.
A beautiful voice is a free voice. Freedom implies freedom from something. Mastering singing means liberation from anything that restricts vocal expression.