This is the hardest thing. You can love friends. You can see the potential they have. You can KNOW there is good IN them, but it means NOTHING if they can't be secure enough to know it themselves. It's like trying to rescue a drowning person, but you know they're going to drown you both if you jump in to try to save them...so you keep throwing life preservers out hoping they'll get a grip and let you help without pulling you under too...sigh.
A woman should never invest in a relationship with a man she wouldn't want for her daughter, nor allow her to treat her in a way she would scold her son for. Emotionally Potty Training Men Are The Biggest Wastes of Time and Energy.