Healing takes a lot of energy, and if it isn't done properly that energy all comes from you. If you use your own energy during a healing session, oftentimes your own personal negativity will transfer over, you become extremely fatigued, and generally there is little success. Where are you taking your energy from when you're healing? Is it yourself, objects, the universe, the Earth? Find what's best for you, and keep your own energy in mind when doing it.
Make sure you're in the right mindset when doing your workings, if you're bothered by your own personal turmoil everything will be off. You need to be in a positive, helpful state of mind, and your spirit should be balanced and healthy. Example: If you're addicted to cigarettes, and you're trying to heal someone of their addiction, you probably won't be as helpful as you would be if you were clean.
Crystals and other healing objects are just tools you can use for their energy, but if you don't know basic energy manipulation you won't get anywhere with healing or other magick practices.