Look before you leap.This is a very famous proverb. The meaning of the proverb is be cautious in your acts. When you are jumping in to a water pond you should have an idea of depth of the pond. Otherwise you will be lost. Similarly when you want to jump over a fencing you should have an idea about the height of the fence. Otherwise you will be left with an injury, minor or major. So one should be careful.
When you have to take a decision you should not do it in haste. You have to use your judgement and assess all possible consequences and make a plan to overcome. Then your success is almost certain. Otherwise the whole mission will get lost in the process. Think twice before you act.
But many people wanted everything to be fast and immediate. Some times this is required. But always you should take calculated risks only.