It's great to be dependable, the person everyone turns to when they need help. But there comes a stage where this turns from a nice thing to the stage where it's just an expectation. "Oh, they'll help, no problem". It's at that stage that you start to realize that you're being taken for granted.
So what can you do to turn this situation before you turn into a doormat that everyone uses but no-one really acknowledges?
Learn to say 'no' every now and then
Ouch - you're so used to saying 'yes' at the moment that a friend could probably ask you near enough anything and you'd do it, no matter how silly the request was. Pratice saying no to the occasional request - maybe someone who isn't a close friend or maybe someone who is really close to you and just assumes that you'll do everything for them the instant they ask.
Call in the occasional favor
You've done enough favors for other people, call one or two of them in every now and then. Don't make a big fuss about it. But if someone you've asked a favor of makes a fuss, gently remind them of one of the many times that you've helped them out of a hole.
Blow your own trumpet
Not incessantly of course, but some gentle reminders here and there of things like how their computer would still be swarming with viruses, how you rescued their critical report or how you turned up in minutes, clutching the missing food from their dinner party. The fact that you're noticing won't go unnoticed by the recipients of your help and can help tip the balance back in your direction.
Be unavailable occasionally
If you're "always there" no matter the time of day or day of the week, maybe it's time for you to not be available every now and then. I'm too polite to say "get a life" but you know what I mean anyway...
Get help
Being taken for granted could be your way of feeling important. After all, if you're always in demand there is a certain ego boost element in play. In your mind, other people need you - that's why they're always asking for your help. It's nothing to do with the fact that you're always available and always say yes. Professional help is one direction you could look but before you go down that route, try hypnosis to help you stop being taken for granted. It's a fast, discrete way to begin your journey to overcome your problem.