Takers will use you for whatever you will give and when a better opportunity or piece of advice comes along, they will bail on you without any gratitude and go in their new direction to take from someone else. The thing to keep in mind is that takers.
Users and Takers are a bummer but a part of life. Lower your expectations and you'll never be disappointed with the negative aspects of human nature. Stay true to your goodness anyway. Good actions manifest into good lives.
The worst feeling in the world is knowing you've been used and lied to.