I written a handful of novels between 100,000 and 200,000 words long, and a whole boatload of short stories (one of which is going to be published in an e-zine soon, and a couple more that currently under consideration--keep your fingers crossed for me!), so I feel like I may be able to offer some advice based on my own experiences!
Staying motivated: just remember there are people relying on you to produce content. Even if you end up with only one reader, well, that one person liked your story enough to subscribe, and they want to see it through. You owe it to that one person not to leave them hanging. Just think about how many stories/comics you've started reading online and fell in love with, only for the author to go MIA and never finish it. It sucks! You get invested in this story and in these characters, and then... nothing.
Thinking about it like that has kept me writing even when I wanted to just throw in the towel and do something else instead.
Which brings me to my next point: you won't always be able to find the motivation. I myself am two days late on an update because I had two lousy days at work and ended up sick today. Some days you just won't want to do it at all. But that's when you think about those readers I mention above, and you get that guilt to get your butt moving.
Sometimes you'll write or draw a chapter and it will feel like pulling teeth the entire time. You'll hate every moment of it, and you'll think "God, this chapter sucks so bad! This is stupid and I hate it and I hate writing and I never want to do it again!"
Most people have those days. You just grit your teeth, power through it, keep putting one word after another until the chapter is done. The motivation will come back eventually, but you can't let yourself just sit around waiting for it to strike, or you'll end up only updating once a month and your reader base will grow bored and leave.
As for being consistent? Commit to an update day. Make promises. Swear on your life that your comic or story will be updated every Saturday or whatever, and do whatever you have to to make it happen. Give yourself deadlines. And build up a buffer! When you have been stricken by inspiration, get as much done as possible while you can. Write two, three, four, five chapters all in one go. Build up your back up, so if something happens and you just can't bring yourself to write anything, you have a few extra chapters already ready to upload on your promised updating day.
One thing that also helps me at least: get out of the house. So somewhere that doesn't have internet. Leave your phone at home. Go to a coffee shop or a park for an hour once a week and just write without distractions. If you have a friend who also writes, get together with them. Spend an hour or two together on Sundays afternoons where you just both write in silence together. If one of you starts dicking around instead of writing, the other one is there to get you back on track. Join a local writing group and go to write-ins. Start your own local writing group and have write-ins! Setting aside special time just for working on your project can help you be more productive than just sitting down randomly and letting yourself get distracted by a thousand other things.