If you limit the ideas or energy you give to your job, I think you'd better be prepared to give those ideas & that energy to your own project quite quickly and in a concrete way.

If your "independent dream project" is too far away on the horizon, you might just get in the habit of holding yourself back from your job, and get used to the idea that you're the type of person who does mediocre work -- and the people you work with may also think of you as mediocre.

So the cost of protecting yourself from being burned can cost you in [1] change of personal habits & [2] reputation among those you work with & know your track record.

Even in times I've been burned with work/life, I've never regretted the effort I put into doing my best at whatever I set my mind to. I've wished I could have foreseen bad events, but not wished I'd tried less hard. I like trying hard... it's fun; I don't just do it for money. Other people can take away the rewards that I may have been entitled to, but they can't tell me that my efforts were mediocre.