Does being an entrepreneur mean that you need to invest all your life savings into the business or project that you're trying to build?

Don't put all your eggs in one basket, no matter how attractive the basket looks like. Never put your bet on one project, so don't invest all your life savings on one idea.

Having said that, you should commit your time in full to your main business to get it successful.

I disagree with this notion.While it is always sensible to save for any future needs or potential opportunities, it would not be a good idea to invest it all in a startup business. Your savings should always be put in a mix of various instruments that have various levels of risk/liquidity.  Even if you are very convinced of the idea, and the potential. Every decision we take has its risks, and starting a business is usually a high-risk endeavor (and potentially high-return endeavor). On the other side, you will never know the exact financial requirement before you have already validated the idea, and possibly tinkered with its possibilities, let alone coming with the actual idea. In many occasions, your real product or service will emerge from a very nominal initial investment, before it requires any further larger investments to scale or to solidify your offering.