I can't because...

So you've always wanted to be a writer, but keep hitting roadblocks. You don't have enough money saved up to quit your regular job so that you'd have enough time to write that novel, and you don't have enough time and energy left after the job, the family responsibilities and the everyday things like laundry, cooking, cleaning and shopping.
Money, time, energy, job, family responsibilities – the list goes on. They are the reasons, excuses and challenges why we can't do something we say we want to do very badly, such as writing. However, you can have what you really want in your life or your reasons why not. Or come to think of it: both.
Here is how. Take a blank page and write down the heading: "I can't because…" Now tape it to your fridge so you can add the next excuse (sorry: reason or even better: challenge) you think of, of why you just can't write today. And underneath, write a creative solution (even a crazy one).
This is my list to help you get started:
CHALLENGE
I'm not an expert in… (take your pick: psychology, gardening, cooking, auto mechanics). All the non-fiction books are written by PhDs with 20 years practical experience. I have this great idea but no credentials. There are hundreds if not thousands of books and articles on the same topic written by people who really know the subject. What's the point of writing another one? Who will publish it? And who will read it? Book and magazine writing business is so competitive.
SOLUTION

Write articles on the subject first. Interview PhDs on the subject. Write it from your point of view as an essay. You are unique and your opinions and viewpoints are different as well.
There are new readers and new magazines every year seeking out and welcoming new writers.
CHALLENGE
What if I'm not good at all? What if I never get published or if I do people will criticize my work?
SOLUTION
Think of Van Gogh. He never sold any of his paintings while he was alive but he kept painting because he was impelled to do so. Keep writing because you want to, not because you want to be published. Or publish on your own just because you want to see your work in print. There is nothing wrong with it. And perhaps once you do, sending your work to a "real" publisher won't be so scary. 
CHALLENGE
Writing is a lonely profession. I need a man (or a woman) in my life first and then I can write.
SOLUTION
By doing what you love to do (writing) you will become a more interesting person and people will be drawn to you. Who knows, you might even meet another single writer. You can join writers' groups or go to conferences and seminars. Also, people will notice that you are busy in a mysterious way and will seek you out.
Write in a public place such as the local library, an outdoor café, or a train station. Many writers have done some of their best work while in public places. Also, see below at the challenge dealing with not having a private place to write.
CHALLENGE
I can't afford to write, I have to work for money. And after work I'm too tired.
SOLUTION:
Write when you can: while commuting, waiting for an appointment, lunching alone. Even fifteen minutes a day will bring you closer to publishing. When you are doing something you love to do, you'll find energy you never thought you had.
CHALLENGE
It's a lot of work and it might never get to see a light of day. At least when I have a real job, I get paid every two weeks.
SOLUTION:
If you work eight hours a day on writing, send something away every week and treat writing as a real job, you'll get paid regularly as well. Even if you don't write well in the beginning, you will learn and improve just like with any other skill and if you have the aptitude and the motivation you will learn faster. You might never write a best selling novel, but a lot of writing is a craft anyone with enough patience and average intelligence can learn.
If you can't write eight hours a day, it will take longer to make any money at it, but if money is your goal, you need to check your motives. No one HAS to write. You need to write because you need to write, not in order to get published and get a paycheck.
CHALLENGE
I start a writing project and don't finish it because I get bored with it.
SOLUTION
Keep several projects going at the same time. Put them in file folders: Ideas and Queries, First Draft, Second Draft, Third Draft, Ready to Submit, Submitted, Accepted, In Print. Often you'll find that you are bored with one manuscript but have a new insight on another one which might have been filed away months or even years ago. And keep the Ideas folder filling up.
Not all ideas will end up completed and published as articles or books, but that's not bad. Keep the juices flowing by not rejecting any idea. And write every day at least one page, just like you brush your teeth every day, even just to get it out of the way. Some days are meant for logistics, such as going through your file of magazine guidelines and updating addresses.
CHALLENGE
I can't concentrate for an hour and then go to my regular job. I have to have an open-ended day to let my imagination and my emotions get involved in writing.
SOLUTION
Plan the book now and think about it in small chunks of time that you do have. Write down the chapter headings, the table of contents, the introduction and the acknowledgements (even if you have to invent them) or for fiction describe the characters and the setting. Without noticing it you will have half the job done. Then, you will be more motivated to spend your weekends and holidays writing the rest.
Or, with a good introduction and the first couple of chapters you might be able to sell the idea to a publisher who will give you an advance so that you can quit that "real" job.
CHALLENGE
I need a place to write, like a room where things don't get moved and where I have privacy. I would also like my own computer that only I get to use.
SOLUTION
Put a desk in your bedroom with a Japanese screen or a curtain to create the illusion of a private room. If you can't afford your own personal computer, negotiate time with your family (or the local library) that is for your use only. And realize that many writers have done their best work while sitting at an outdoor café or waiting for a train with a pad and pencil.
Also, see the solution to the challenge of feeling isolated as a writer, above.
I agree, it really is difficult to write with all the rest we have to do in life and especially with no guarantee of publishing. But if we recognize that problems are really only challenges in need of solutions, success is ours and our dreams can come true.