I think there is a difference here between a 'fortune teller' and an actual psychic medium.
Sometimes it can depend on why you are visitng one. For example 'What is going to happen in my love life?' Well, anyone can tell you what they might or might not see/here etc from the other side, or even from the tarot cards etc. But, ultimately your future happens based on your choices, so if they tell you - yes I see a man/woman ehatever and a, b, and c will happen - then that is only what they can see 'might' happen. There are so many choices in your life that if you take a different route/decision one day, then your future could potentially change. I don't think anything is set in stone.
You may wish to see if you can receive a message from someone who has passed over. This IMO is different from being told your 'future'. If you received a message from someone and could validate it, then this could be comforting?
I have seen several psychics in my time, and some things have rung true, some have not. I wasn't visiting to get any vital life making decision help, just to see what they could see and if there was any truth in any of it. Some things have amazed me, and I know that there is no way specifics could have been made up - they relate directly to me. I have also received messages from loved ones who have passed on via mediums.
People who are psychic/mediums etc can receive their information in varying forms. They may try to interpret what they are seeing/hearing and convey this to the recipient. Sometimes it gets lost in translation.
Sometimes to find an answer all you have to do is look deep inside yourself, no fortune teller can tell you what's going in there.
Just my opinion 