Three common problems
How to fix a cocktail that's too sweet, too sour, or watery
These three problems cover most cocktail balance issues, and the fix is rarely 'add more of the thing you think is missing'.
Every recipe on this site has its own "Rescue this drink" section with fixes specific to that exact build, but the underlying causes repeat across almost everything you'll make. This page pulls those three recurring problems out into one place.
Too sweet
Almost always a citrus/dilution problem, not a 'less sugar' problem.
Before cutting a sweet ingredient, try adding a small amount of fresh citrus or a splash more of whatever's giving the drink its sourness — most cocktails are built around a sweet-sour balance, and it's usually easier to add acidity back than to rebuild the whole ratio. A touch more dilution (a few seconds longer stirring or shaking) also softens sweetness without changing the recipe.
Too sour
Usually needs a small amount of extra sweetener, not less citrus.
Fresh citrus varies a surprising amount by fruit — the fix is almost always a small addition of whatever sweetener the recipe already uses, added in small increments and tasted as you go, rather than reworking the citrus quantity.
Watery or weak
Almost always over-dilution — check your ice and your timing first.
This is the single most common cocktail complaint, and it's rarely a recipe problem: small or partially-melted ice dilutes faster, and shaking or stirring for longer than the recipe calls for adds water you can't take back out. Check both before assuming the ratio itself is wrong.