Bitcoin growing its value (deflating) is precisely the problem because then you have no reason to take the risk to invest in the first place since you'll reap the benefits by merely doing nothing and holding your coins that keep getting more valuable.

At the same time, it allows you to put brakes on your investment ("lose only up to the deflation!") and invest more. And since your other savings are growing in value as well, you are able to invest more and into more risky projects.