Punishment is an awful way to motivate anyone, yourself included. The reason we think it works is because that's how everybody else in our lives treat us: parents, the school system, employers, financial institutions, etc. We get to the point where we think we have to be abused in order to perform, like whipping a dancing bear.

Trying to motivate with punishment leads to value judgment, leads to guilt, leads to mental avoidance.

Avoidance involves much less effort than actually doing the work.

Which is the real reason that it's hard to get personal projects done.

One other reason is that people talk themselves into doing personal projects because they "should," not because they're fired up. And lastly, burn-out from the should-punishment-guilt-avoidance cycle makes it hard to get motivated.

When you get out of this cycle, when you cut yourself a break, when you stop "shoulding all over yourself," magical things can happen... and you can devote regular time to things because you love them, without breaking out the stick or the carrot.