The thing to remember about people, when you're at your worst: feeling lonely and insecure, there is always going to be someone there ready to use that for her own purposes.
It may seem harmless, someone who just wants your attention a little too much. The person may be in a bad way herself, and you feel you should be there for decency's sake, because that's what you'd want, because you shouldn't judge. You can even understand where she is coming from. If the roles were reversed you'd want someone to give a shit about you even if the attention is half-assed like yours.
But you know what? If it doesn't feel right you shouldn't do it. That's it, period.
It's not going to help your insecurity or sense of inferiority or fucked-upness to sacrifice yourself for someone else. Especially not someone who can't back off, give you room to breathe, or take a look at her actions and ask herself if she is asking too much. In fact dealing with people who has figured out how to use your inability to say no and your guilt to get you to reluctantly agree to even to most innocent of activities can only make you feel worse about yourself.
How can doing things for someone, or with someone, who refuses to accept the boundaries that you set up, ever make you feel stronger and better? Isn't she rather increasing your sense of uselessness by confirming that what you feel is not important? In fact, isn't she telling you that all that matters is how others see you, and what others want, because you are no longer competent to judge?
It might give you something at times. You probably think it's worth it. Maybe there are moments of tenderness, of understanding, of closeness, but if on the whole, you want to withdraw, would rather be alone, would rather be dead because all your relationships are like this: people trying to make you do things, make you be someone, or just refusing to acknowledge you as a person, with feelings and innate value, then you got it wrong.
You may think there is only loneliness if you tear these people out of your life. Indeed, they're your only friends. Without them you're the horribly lonely cat-lady. And really, on your good days, it doesn't feel bad to indulge them at the expensive of you. It makes you feel generous.
But you are wrong. The only thing they're doing is sucking away the energy you need to reach out and form normal, healthy relationships with people who do not only take but also give. They are out there: the co-workers that seem nice, but you never get a chance to talk to because your time is always monopolized by someone else; or that instructor in that drawing class that was so concerned when you never showed up again that he called to ask where you'd gone.
Or those friends whose messages you never returned, who have given up on sending you more. They're still there. I promise. They liked you once; they're willing to pick it up again. No, they may never understand what's wrong with you, maybe they'll be more distant, but they'll still be your friends.
So, it doesn't matter if you know how the leeches feel, if you can understand how they struggle, if you see and feel their pain, or if you feel so intensely connected that nothing can replace it. You cannot let people suck the life out of you.
You may have felt like a leech yourself at times, and you may have wished for understanding, and felt overwhelmingly abandoned when you didn't get it, but honestly, if no one was willing to let you bleed them you shouldn't let someone else bleed you. There is only so much we can give, the rest we must save for ourselves.
And if you're here, chances are you have even less to give. Your own mind is your enemy, it's like a stormy sea of emotions all on its own. Don't add other unstable personalities to the mix. Try to find safe ones, who know themselves, who can offer you limited but assuring attention instead of brushes with insanity.
I am counting on you, if you can do it, so can I.