How do you turn it off and forget about the ability?
The truth of the matter is you can't simply turn it off and forget it. The simplest analogy I can think of is if you wanted to stop eating, because you want to lose weight. You can certainly cut down on eating, or eat more wisely - but stop eating altogether, and you won't be around too much longer.
Your psychic ability is tied to your intuition, creativity and intelligence. The only way to totally turn it off is to stop thinking. I can think of a few blonde exceptions to the rule ... but most of us need every advantage we can get, and by totally turning your back on this gift, you will deny yourself and the rest of the world many valuable insights along with the challenges. not only that, but in my experience, the harder you fight to stuff it down, the more intense it will get until it breaks through, usually in chaotic ways.
You can learn to accept it, to learn from it, to control it better over time, though. If you have frightening visions, the more accepting you are of the experience, the more positive they will become over time. If you fight, resist and deny it, it will find other ways to express itself in your life. You are far better off working with it than fighting against it.
I wonder though if "how do you turn it off and forget about the ability?" is the real question. I suspect the real question is deeper than that. If you are unhappy with your psychic experiences, chances are good you are unhappy with other experiences in your life. I find that depression is all too common amongst hyper-sensitives.
I did find that Prozac helped me "shut down" my psychic abilities during one particularly difficult period of my life, but if I could go back into that time, I would change many things I did, including taking a dangerous, expensive, potentially addictive drug to escape my feelings. What I have learned since then is that my attitude towards life has a huge impact on the quality of my psychic experiences. As I have become a more happy, joyful, fulfilled and confident woman, I have also developed more control over my psychic abilities.
What happened was that I took The QuinnTessential Experience class, and it totally changed my outlook in life. I have now lived without depression for more than four years. It also had the side effect of giving me a set of growth skills I needed to finally get real control over my psychic abilities. When I began to develop a happy, confident, effective mental outlook, everything else fell into place naturally. The class costs less than a year's supply of Prozac, even accounting for travel costs from most places in the US and Canada. Even though this class has absolutely no content strictly related to psychic ability, if you are unhappy with your experiences, it is the fastest way I can think of to turn your life around.
If you can't get to The QuinnTessential Experience, the next best thing is to read my book. Study everything you can get your hands on about meditation, grounding, and psychic protection. When you have a frightening vision, write it down. Go back to it later on and look at what you wrote. You will have insights that will help you better accept and understand your visions. Reach out to others, though the discussion groups here and at other psychic protection sites online. Knowing you are not alone is a huge step towards acceptance, and that is the thing that will help you the most.