Just invest what you can afford to lose, it's always risky to invest in bitcoins or any alt coins because no one knows when it's going up and down. So if you want to invest in bitcoin learn first how the flow of it in the market, and just have to be updated from time to time because leaving it for just a minute you can lose all of your resources and capital. But holding bitcoins for the long run can give you a chance of having huge income someday because everyday bitcoin's price is increasing.
I totally agreee with you, invest what you can afford to loose is the main rule