Predictions of the future are not always able to changed no matter what you do or who it is that is trying to stop it. There are many pathways to the same point in time, sometimes people think that they can stop themselves from getting in a car accident by taking a different route to work and then they end up getting in an accident anyways. So then you have to wonder, would they have gotten in an accident at all if they would have went the normal way? IMO, there are certain events that are destined to happen, good and bad...actually, no event is good or bad really, it's neutral, perspective makes it good or bad...anyways, these events have to happen and they can't be changed. You can basically change which road you go down but if it's a destined event, all roads lead to the same place.
Then there are predictions that can be changed. These can be warnings telling you that you are going down the wrong path and to avoid unnecessary turmoil you need to change your direction. There are also foretellings of good things to come and to be extra careful about how you treat a certain person. This person could be a future mate but it wont appear that way at first or it could be a very influential person that you are unaware of and they are going to open up doors for you etc.
Then there are also probable futures. Sometimes there are a number of futures that can happen, one being ideal, the ones in the middle ranging from positive to negative, the last one (furthest from the ideal one) is the worst case scenario, the worst probable future. When someone is faced with probable futures like that, it is their actions that are shaping the end result. These time periods often have to do with learning life lessons and karmic situations. The more one has learned and is aware of such things happening at that time in their life, the more they are willing to settle their karma...the more likely they are going to end up somewhere closer to the ideal outcome or even more fortunate, the ideal outcome itself.
Reality can't be warped by humans. There are Universal laws in place that prevent that from happening. Although our world may look chaotic and random at times, that is an illusion. Everything is always in Divine perfect order at all times.
Any accurate information that a psychic gets about the future has been allowed to come through. The psychic is not piercing through boundaries or getting around Universal laws. She or he is a part of the scenario just like all the other players, the psychic does not stand outside of reality and orchestrate, they interact within the realms of what may be, what will be, what is changeable and what isn't.
*edit*
To whoever gave me a thumbs down, I challenge you to take the time to write a well thought out answer.