I'll save you the time of getting an MBA (note this primarily applies if you are building a B2B product company, consumer is much harder to validate):
Before you start your new company, figure out what your product is, then figure out who will buy it (I mean, who is the specific person in an organization that would need to make a purchase decision). Then, go talk to 2 or 3 of those people.
At this stage, if you can't figure out who those people are, then you have a problem that isn't going to go away once you've spent 12 months building your product. You have no market, do something else.
If you can't get a meeting with those people, then you also have a problem that isn't going to go away after you've built your product. You can't penetrate your market, do something else.
When you get a meeting with them, don't try to pitch them your idea. Tell them that you are exploring a market opportunity, and that you'd like to describe a product and ask them if they would buy it. Make it clear to them that they are very welcome to say "no, I won't buy that". In fact, you should try to get them to tell you they won't buy it. If they tell you they won't buy it, your market doesn't want it, do something else.
If they say they'll buy it, ask them if they would sign a non-binding letter of intent saying that if you build the product, and it does what you say it will do, that they will purchase it. This commits them to nothing, but these LoIs are gold if you are ever pitching investors. They are also a robust sign that they aren't just telling you what you want to hear. If they won't sign LoIs, then they weren't serious when they said they'd buy your product, your market doesn't want it, do something else.
Get 2 or three LoIs in your back pocket, then you're ready to quit your job and start your business.
I guess the key idea here that most entrepreneurs miss is that you really need to vet your own ideas. Many aspiring entrepreneurs dream up an idea, and then stick to it doggedly, either because its the only idea they have, or they find it technically interesting. They don't want to discover that it won't work, so they don't try to figure it out! This is a bit like writing some code, and then not testing it because you really don't want to discover that its buggy.
The one thing worse than not starting a company is wasting 6 or 12 months of your life on an idea that has no market. Be smart, and do your due diligence on your own ideas before you take the plunge and start a company.