My ball toss goes everywhere during high-pressure serves. How do I lock it down?

Practice serves are totally fine, but the second I hit a break point or a tie-breaker, my toss becomes a complete joke. It either drifts way right or goes too far forward (I'm a rightie), leading to massive double-faults. I’ve tried the standard 'holding a glass of water' tossing drills, but my mechanics still crumble in actual matches. Need solid mental cues or mechanical tweaks to stop tossing like a nervous rookie when it actually counts.