I've been having some great ideas lately, they're all short bursts of fragmented scenes for a story but I think I can manage to build it up to something comprehensible. But the thing is, I don't think I won't be able to handle it properly, not with the work schedule I'm currently into. When it comes to situations like these what do you do? If it's hard to keep the balance between working and writing how do you handle it? 

Write on the way to work or when you have breaks. Be careful though some companies can take the royalties because you did it on "their time".

I use that as an opportunity for all the tiny bursts in a big idea to sort of inch together and meld and gel into a whole thing. If I'm busy, at least, my subconscious idea for the flow of the story is sort of...percolating, like coffee.

So, I don't worry about it too much.

The thing is, we're used to this image of a writer of doorstopper adventures, literary fiction that defines a generation and remains an influence on the philosophy of an entire civilization--as somebody who does all that on their own. It can't hurt, surely, to develop plotting skills, writing style, and characterization...but, I can also see how some people can be good at ideas but not so much the execution. Or, some people have the best style and voice, but no mind for plots or how to direct it.

Oftentimes, in the industry, there are outliners and ghostwriters who collaborate to publish under a pen name. I think that's fine, as long as the finished product is still entertaining. So, maybe that's something to consider if you get too intimidated by the requirements of the ideal writer-artiste.

I think that is awesome that you have an idea for a big story, and you should definitely work on it while the idea is strong in your mind. Even if you can't actually do the writing because of your schedule ,  at least make some reminder notes, so when you have the time to write then the notes will ring everything back fresh in your mind.
I try to do this because even when I have an inspiration that I am sure I will never forget, and I don't write at least some key notes down; then when I try to write it, I have lost the flow of the thoughts, and can't remember exactly what it was I was going to write. When I have some notes, it seems to help put me back in the same frame of mind as when I had the idea.
Maybe this will work for you, too ? ?

Also try not to focus on "making it big" and focus on the story. Maybe it will be big, maybe not. I've found when trying to make a "big" story I've actually ended up stressing and killing it. When I am writing a story for the stories sake I find I am more able to make it a nicer length based on the story and the feel.

There's no shame in a short or medium story either. Better a well written medium story than a badly written or overly verbose long story ha ha. (also don't worry too much about editing at first, just get the story written then edit it )

Are you on any type of timeline for these big ideas to come to fruition? Only asking because I don't think you should let life, work, school, family commitments, etc. get in the way of what you want to do. (Easier said than done, I know, but I would hate for you to get discouraged.) If you are really concerned about time, but these awesome ideas are flowing I would slow it down a bit. I suggest writing everything down, maybe even having a loose outline because this way you can take your time, but also don't need to worry about running the risk of forgetting anything. When life gets in the way of writing I try to employ this habit and it tends to work. I think sometimes the idea of trying to juggle a large writing project with work can be somewhat daunting but once you start moving forward it may become manageable or you figure it out as you go along.

Good luck on your big adventure.  It is hard sometimes to make time to do you life, such as working and taking care of kids, and then having time at the end of the day to sit down and write.  I am looking to write a book as well, but right now I am just in the outlining and note taking phase.  I carry a small notebook with me that will fit in my purse so that I always have paper on demand when a good idea pops into my mind. 

I also use my notebook to jot down ideas if I want to do some research later.  If I hear about something interesting, or a website I want to check out later, it goes into my notebook.  What kind of book are you going to write?