“Let children experience the frustration of making mistakes.”
When they spill, be sure they know how to clean it up. Help them as needed.
If they can’t make something work right, give them a chance to try again – and again and again, if need be.
If they can’t figure something out, don’t jump in with the answer. Let them struggle – that’s how they will learn. If they seem stuck, ask them a question that will get them thinking in a new direction.