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
Any long-term investment should be comfortable, only in this case you can be consistent throughout the investment period. If it is, as you said, at any cost, then this implies that we will most likely need to make some sacrifices from time to time, which in the end will make us doubt the correctness of our actions. You also don't need to invest all your savings, because various situations may occur that require us to unplanned expenses and in this case it will be necessary to sell part of the investment, which is also not very good.