Alex took spent the last year and a half creating his course, The Ultimate Guide to Understanding DOM Events, at egghead. Finding the time to work on a side-project like this isn't easy, and it requires one to examine their current priorities in life. Do they want to be a rockstar developer? Or do you want to have a lot of free time to spend with your family?
No matter what sacrifices have to be made. But the best way to handle it is to have candid discussions with the people around you who will be affected the most by these sacrifices. Alex worked it out so that he'd work on his course one day a week.
Despite the cost in time, side-projects are important to Alex. He says that he wouldn't be where he is now in his career without them. They enabled him to grow as a software engineer and to learn things that he wouldn't be able to during his day job. Because of this, he was able to get a more complete picture of how all the pieces fit together, which made him a better dev.
So remember, really be careful about what you are committing yourself to when you take on a large project.