I Think I See Dead People

You can just tell it to leave. If that is what you command, it has to follow. I've dealt with a few scary ghost experiences, and my friend (who has the same abilities as me) told me this when I came to him all freaked out. Also, if you find some source of protection, like a gemstone, it would help, too. Mine is a key, which also keeps the sightings on low key, because the spirits seem attracted to me and I see them all the time if I take my key off.
Keep talking to that guardian angel, too. They always help; they're just waiting for us to ask them to help us. And I know it might seem really scary at the time, but most things can't hurt you. And I like your dog. Mine just sleeps through all of my encounters. That is a good dog.
The white figures were helpful spirits, or some higher being with your welfare in mind. I completely agree with Noriko1111 on her take on things.

You're story's creepy:s I've ever saw a shadow of a ghost accidentally in front of a school locker, and in my old house. But now I don't anymore. I used to be able to sense if there's a ghost around, but I think now the ability is gone.

I can do that to and it freaks me out sometimes that they just stare...
But I can also feel their presence a litle while before they arive, so I'm a little more prepared but it still catches me offguard someimes.

The white figures are spirits. Some are people who passed away, angels, other unknown spirits while the second half that you were scared of were possible wraiths, demons, very angry or malicious person or dark spirit, etc... The feel and the colors are something to go off from. All pure white warm spirits are good and they all have a unique personality. All black aura like figures are possibly demons or people who have very dark feelings. Majority of them has a great hatred, anger, jealously, etc... Feel to them or just plain overwhelming powerful (its hard to explain). Grey color tends to be depressed type of spirit usually around people who committed suicides or spirits that just depressed all the time. There have been cases where black and white type aura like figures have been seen as well as different colors. All spirits that you see have their own personality.

When you feel threatened it is best to leave that area. Some dogs are able to see things that people usually can't see. Even dogs have their own set of abilities but not every dogs can see the otherside. You do not have to be scared. You will continually see spirits in the future, don't let it upset you. Its a double edge gift/curse, how you use it is up to you. What important is your not insane. Some people can see spirits, others can feel emotions, other can see the future, or taste or smell things, etc... There is nothing wrong with that.

The benefits or curse (depending on how you see it) of being able to see is that it will help you stay away from certain area's you feel wrong by the spirit that are residing there. Other times there will be an overwhelming lure to an area, (depending on how strong the spirit is) who is malicious or good. Certain houses, areas, buildings etc... Have pretty malicious spirits living in them, not all or the opposite is true. People who have a guardian angel, (some people don't always have one when they are born, but they are assigned to one depending on their life path.) you will be able to see a quick glimpse or see your deceased family members and friends. Sometimes with the ability to see, the ability to hear what they say can come naturally.

If you ever do want to take the path to dive into the metaphysical and learn how to protect yourself just ask around. That is a whole lecture in itself.