Pagans and Witches usually believe in some form of what's called the Witches' Rede: "As long as you harm no one, do what you will." That isn't nearly as easy as it might sound. That means whatever action you undertake, it can't harm anyone, including yourself. Witches and pagans also believe in some form of the Law of Return: "Whatever you do magically [or otherwise] will come back to you," some say three times, some nine, some just say it will come back to you. And it does. As Ursula K. LeGuin said, "You can't light a candle without somewhere casting a shadow."
Most of us believe that it is wrong to use magical power to coerce someone into doing something against his or her free will. Curses and love spells are the most prevalent examples of manipulative magic. Some Witches and pagans do believe that using one's powers in defense (say, to assure a rapist's getting caught) is all right; others do not. Those who do choose to work that kind of magic do so knowing that it will come back to them, and are making an informed choice when they decide to do so.
This makes it sound as if we spend our lives deciding whether to curse or hex someone, when that's not true. Most of the time, our spells and magical workings are for such things as healing the planet, getting a job (or otherwise bringing prosperity into our lives), healing (both ourselves and others), and spiritual empowerment. Spells are really quite similar to prayer -- they just have more Hollywood hoopla attached to them.
Besides, anything you do for yourself will work much better than a spell or working done by someone else.