When your business is going great, you will be asked to do a lot of jobs and that is great. But be careful, you don't accept more work than you can handle. If you are mis a deadline you could be missing out on that client. So dealing with deadline is as important as being a kick ass audio engineer/producer.
My project co-ordinator often calls me and ask me how much time I think I need for a certain project. It could be anything from recording and editing a commercial voice-over spot to just doing some pitch corrections on a song. Even though I am a professional and know for a fact that 95 times out of 100 I could do an edit or whatever in for example in 2 hours, I always tell them that it will take about 3 hours. If it is a bigger project that should take 3 weeks, I would tell my project coordinator or client that I need 4 weeks. I just want to be certain that I can deliver a top notch product. It doesn't matter if you are really awesome on what you are doing. Your skills wont help you if your computer decides to stop working or if something else unpredictable happens. That's why it's always better to have some extra time.
Clients Don’t Care
Most of the clients don’t care about the reason you missed a deadline. They don’t care if you had to work 24 hours the last few days to deliver in time. And they sure as hell don’t care if your girlfriend or boyfriend just broke up with you. All they care about is that you will honour the promise you made when you took the job - to deliver it on time. If you know that you can't deliver in time, don't take the job. It's always better to say that your schedule is full.
Get Things Done
Don't wait to finish things on the last day. It can put you in a position where you have to rush things, and leaves you no slack if something goes wrong or something you weren't expecting crops up. Remember that all jobs/mixes/recordings are your CV. And you definitely don't apply to a job with a CV that you are not one hundred percent satisfied with. In this business your reputation is your CV and a good reputation will bring you more possibilities.