Yes absolutely, I also recommend to hold, but keep in mind it will go lower and lower for another few months.
People here who are still hoping it will jump back to $1 within the next days or weeks are dreamers. Try summer 2018 at the earliest.

I also find it funny how people said that it will never sink below $1 again. Then it went to $0.90 and people said not to worry it will not go lower. Then $0.80, then $0.70 and now it's at $0.60 and people keep dreaming it will go up to $1.00 within a few days.

No! No that won't happen. But don't freak out, and hold your investment. If Power Ledger does indeed manage to deliver on their product, in 6-12 months it will explode again by 500% - 1000%. Until then, it will probably fall back to $0.30.
The absolute worst thing that can happen, is that Power Ledger will fail to deliver and go bankrupt, or a competitor will beat them to the market, that will make POWR be rendered worthless. But that chances of that happening, is smaller than their potential success.

If you invested everything you had and you can't wait 12 months, well then cut your losses now, if you can hold it for 12 months, then don't sell. Easy as that.