People hate excuses. Missed deadlines generate excuses faster than dogs eat homework! When you are asked to undertake a project, understand the expectations. Be forthcoming with your questions about the parameters and purposes of the project. Get as much clarity as you can about what your boss is wanting from you specifically. Discuss the projected timeline in depth. Take time to consider your ability to meet the schedule. Agree to produce only what you are willing to deliver, what you CAN del.