It is common for founders to "discount" their time when they work for the company.  They might work for discounted compensation (to show hard work and goodwill), or work for free, even when others are getting paid and even when there are investors.  As a founder, it is tempting to believe that "magically" everyone else involved in the company (other founders, investors and employees), will value this contribution.

This is almost never the case.  There is no "magic" in a startup.  That old saying "why buy (pay) the cow if you can get the milk for free" has relevance here. 

Instead of contributing time, consider "investing cash", and then getting paid for time.  At the very least, set a market compensation rate, agree to take a discounted compensation and then have an explicit agreement that exchanges the value of that forgone compensation for equity or for an increased or accelerated grant of options.   Be explicit with your investors and fellow founders that you value your time, and they will too.

This flies somewhat in the face of the idea that "you own a big chunk of the common stock" and that's how you'll get rich - but it pays to take into account a variety of exit scenarios when valuing your own time.