Bitcoin investments is a very promising investment which although seems to be of long term returns.most persons are not patient enough to wait till the value of Bitcoins rise significantly .
Soo in general how much should one invest in Bitcoin should it be "how much you can easily invest without stress " or "as much as you can invest at all cost"
Although I am aware it isn't a do or die affair
In accordance with your goals, you can invest in Bitcoin according to your abilities. Don't push too hard if you doubt that the money you invest will be lost, because actually investing in Bitcoin has risks and if you can't take that risk you shouldn't invest, it's that simple. If you can invest 100 USD in a month and have no problems with it, you can invest that amount, or less. The point is to adjust to your abilities, that's all.