Why do you have to use amounts of money that make you uncomfortable? A good position should end up becoming big vs. the lesser positions mostly on its own merits.
Yes the stomach and patience are hard. Basically because you will never be sure.
Because if you're comfortable, it's probably because either you aren't trading enough for it to be worth the time (it's a hobby) or you have so much in the bank that trading performance is mostly about whether you can afford a Monet.
Avoiding stress, in the context of this discussion, for me involves not giving "tips", doing your own money, accepting and sometimes loving volatility, taking losses and accept undergoing periods of not looking like part of the winning team (which I think is what the original article is about), avoiding irrelevant constraints, and obviously avoiding ruin at all cost. But you can't get around doubt.
Having proper income for daily life and budgeting for setbacks is a different discussion. That's an issue you must get in order prior to investing. It's a prerequisite.
Yes the stomach and patience are hard. Basically because you will never be sure.