Since my grammar class, I've always learned you have to use
for oneself - on one's own, by oneself- alone.
1)Tom does everything for himself - on his own
2)Tom lives by himself - alone.
But I rarely heard native speakers say for oneself, by oneself, and they seem to use just oneself more like
1)Tom does everything himself.
2)Tom lives himself.
but oneself is to emphasize one's action, so how can you differentiate emphasis and these usage if you only use oneself?