Want to start your own business? Consider keeping your full-time job for as long as possible. Here’s how.

Arnold Schwarzenegger says you should keep your full-time job while you start a business. So does Richard Branson. So does Harrison Ford.

So do I; when asked, I almost always tell aspiring entrepreneurs they shouldn’t  quit their jobs and go all in on starting a business. Before you give up your steady source of income, prove your idea for a business works. Prove you can land, and satisfy, customers. Prove you can actually generate revenue, and make a profit.

To pursue your entrepreneurial dreams while minimising risks and maximising your chances of success, keeping your full-time job is almost always the best approach.

Of course, it’s also the hardest approach: Sacrifice, discipline, and a massive amount of hard work are required - and that’s a good thing. In addition to proving your idea for a business works, you can land customers, and you can make a profit, see keeping your job as another major test. If you aren’t willing to work hard and make sacrifices, your new business will fail whether you keep your full-time job or not.

So how can you keep your full-time job and make your new business a success?

Slash your personal expenses

Almost every business venture requires spending money before making money. Unless you have significant savings, some of your seed money will need to come from your current income. If your business takes months to turn a profit, some of your operating expenses may also need to come out of your current income.

A major percentage of startups fail because they run out of money. Even if they don’t, chronic money problems can lead to poor long-term decisions. As Arnold says, “Preserve your power to say ‘no.'”

Never assume personal savings will see you through. Eliminate every bit of personal spending that isn’t necessary so you can make your financial runway as long as possible.

Keep the main thing the main thing

Trust me: As you build your business, you’ll be tempted to slack off at your full-time job. (Plus, your startup will seem like a lot more fun.)

Don’t give in to that temptation. When small-business capital and cash flow are tight, losing your full-time income is the last thing you can afford. Make sure you stay indispensable. Work hard. Work efficiently. Go a few extra miles.

Why? For one thing, you owe it to your employer. For another, you don’t want to raise concerns about your performance or dedication. And you want to be able to someday leave with no regrets, and no feelings of guilt, about how you performed while you started your business.

Create and stick to a demanding schedule

When your full-time job workday ends, your startup workday will begin. So start by deciding how many hours you think you can spend on your startup every evening.

Then add 25 to 50 percent to that number. And then commit to that schedule. If your schedule says you will work from 7 p.m. to 9:30 p.m. every evening, and from 7 a.m. to noon on weekends, work those hours. See the schedule you create for your startup the same way you see your schedule for your current job: as nonnegotiable.

Then put your head down and do the work. Success in almost every pursuit comes down to time and effort. Be the person who puts in the time and the effort.

Reframe your work hours as an opportunity

Working 12-hour days (split between your full-time job and your startup) might sound daunting. Might sound like a grind. Might sound like a burden.

Resist the temptation to feel sorry for yourself.

Say you start a consulting business. Once you land a few clients, you’ll be working every evening and most weekends. That’s not a bad thing, it’s a good thing, because landing clients means you generate revenue. Sure, you may have to get up early every day to take care of emails and voicemails before you head off to your job. You may have to respond to emails and inquiries late at night.

That’s not a burden. That’s an opportunity, because needing to respond to clients means you actually have clients.

The hours you work on your small business are an opportunity to build your business, and build a new life.

Reinvest your profits

We all want to be rewarded for our work. We all like a little extra money. When you start making money, you’ll be tempted to spend it.

Don’t. Embrace the bootstrapping mindset and reinvest every dollar you earn. Use the money your business earns to create the business infrastructure you need (not the one you want, but the one you need). Buy supplies. Buy the equipment you’ve had to rent. Increase your advertising budget. If nothing else, save some cash to tide you through the inevitable revenue downswings.

The more your business can fund itself, the less you need to draw from savings or from your employment income - and the longer your runway.

Don’t quit your full-time job too soon

Deciding when to quit your job and go into business full time is one of the hardest decisions you’ll make. It’s impossible to make an objective decision when you’re tired, stressed, sick of your full-time job, sick of your boss, or just want your life back.

But don’t quit too soon. When in doubt, hold out. (I kept my full-time job nearly a year longer than I wanted to; while I didn’t enjoy that time, I’m really glad I did.)

Prove to yourself that you can generate consistent income. Prove to yourself that you can continue to broaden your customer base. Prove to yourself that your business will grow when you have more hours to devote to it. (You may be able to find a steady supply of customers for a 20-hours-per-week business, but can you land enough to feed a 50-hours-per-week business?)

Let the numbers indicate when it’s finally time to quit your full-time job.

Not your emotions.