How many is too many?

With toms and cucurbits, in the past I've usually sown 4 to a small pot then had too many. I can't be ruthless at seedling stage, I just can't. Then when I've possibly let the extras get leggy/potbound/starved and I have no room they get composted, no one round here wants them. This year I've only sown 2 per pot, which is a bit of a shame as I've found a pen pal from a few villages away who is willing to share. With flowers, where I'm no use whatsoever, I sow and fail no matter how many. Beans it's not the qty of seeds but the number of varieties that cripples me. I want to sow them all! Beans never get composted there's always a spot for a bean.
I've currently got two pots crammed with helichrysum that need pricking out, they'll all get a chance.