I can totally see where you're coming from here, but I think you're running into the same problem I do a lot - spending more time pointlessly panicking about lack of time than you do actually drawing the thing.
I have sleepless nights when I worry about getting things done on time - and then I get up in the morning and manage to have the thing I worried would take DAYS all wrapped up and done by lunch.
What I'm saying is that step one is to stop worrying and just do.
Step two is to adapt the scope of your project to suit your needs and available time. Making comics is a good way to give yourself a regular thing to work on; it instills discipline, and allows you to put all those art-fundamentals into practical use. However, you don't have to jump in the deep end and do a 1000-page epic from the get-go. You don't even have to do a 150-page graphical novel! You can do oneshots of 25 pages or less, and still get the practise in! It's a smaller time-investment, and you can set yourself a deadline you're more comfortable with.
That way, you will still be able to take the time to do all those illustrations and practise-pieces. And with a oneshot, you don't need to worry as much about doing it super-fast; if you do 1 page a week, a 15-page oneshot is 3 and a half months of your life. That's not actually a whole lot, if you count up all the other stuff you'll be doing at the same time. You need to be thinking about the fact that you WILL need days or nights off, time to spend with your family relaxing and doing something just for fun, too.
You will get faster as you go along. You'll pick up time-saving tricks, you'll get used to drawing your characters, you'll get more comfortable with your chosen tools, etc., etc. When I first started drawing comics, one page a week was about what I could manage - these days, I manage a regular webcomic updating twice a week with full-colour pages, loads of single illustrations, some commissions AND oneshot comics on the side, and still have time to laze around on the couch a couple of nights a week. That kind of speed won't happen overnight (it took me about 10 years) but it IS possible to get there.
Don't stress, don't worry, and just do. It's okay to be slow at the start, it's okay to work on smaller projects, it's okay to just do things at your own pace. You won't get awesome by rushing it.