haste
Rushing to do something so fast you may mess up.
Haste means hurrying or rushing to do something quickly, often too quickly. When you act in haste, you're moving so fast that you might make mistakes or overlook important details. A student working in haste might skip reading the instructions carefully and answer the wrong questions on a test.
The word carries a warning: speed isn't always good. There's a famous old saying, “Haste makes waste,” which means rushing often leads to errors that create more work later. If you build a model airplane in haste, you might glue pieces incorrectly and have to take it apart and start over.
Haste is different from simply being quick or efficient. A chef works quickly but carefully in a busy kitchen. That's skill and practice, not haste. But if that same chef rushed through the work carelessly, that would be haste.
You'll often see haste paired with other words: someone might make a decision in haste and regret it later, or leave in great haste when they're running late. The related adjective is hasty, as in a hasty decision or a hasty retreat.