most persons are not patient enough to wait till the value of Bitcoins rise significantly
The best strategy to make huge profits from Bitcoin investment is to be patient and able to hold for a long period of time, but still everybody have it own target in term of Bitcoin investment, once someone reach it profit target I think that is okay to take the profit. sometime we don't need to wait for long term to take profits because there is not guarantee over our Bitcoin investment that we will make more profit in future but we do assume it will happen because the repetition of Bitcoin history.
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
No to be stress in your Bitcoin investment, someone need to invest on what it can afford to lose. Let know that no amount it small when we lose it but that always depend on the investors.