Not more than you need yourself. That's "unbalanced". You can't give (needing someone else is giving yourself and your energy/"power" to them) more than you retain or you'll fall over :-)

Of course, if you're met with the same from the other person, then that's a team and you've got a partnership and you're fine until one or the other "leaves" and that's where grief enters into the equation. You have yourself invested in the other and have to slowly get it back so you can reinvest in someone(s)/something(s) else.