I used to do a lot more with music, but with art taking 99% of my time I've had to let go of most other hobbies. Not a bad sacrifice IMO haha. I find that songwriting especially is a matter of inspiration, certain feelings or a tiny idea or chorus sparking an entire song, I wouldn't know how to do that under a deadline either, it comes as it comes.
The point with deadlines is that they also help you keep limits, and thrive within them. Creatives often forget that 'work smarter, not harder' counts for them too. At least, to an extent, it can really help you get motivated to just get it done and over with so you can move forward again.
Douglas Adams said that he loved deadlines. He liked the whizzing sound they made as the passed :)