This is one of those tricky things. We love knowing that we have free will, it keeps us from feeling trapped and helpless in our lives. But at the same time when we ask for a tarot reading we ask "What is our fate". These two concepts seem to be almost mutually exclusive because if we have a set in stone fate how do we also have free will, and if we have free will how do psychic readings even work in the first place.
It might help if I were to explain my understanding of it and maybe it will help answer your questions.
I believe in both fixed fate and free will. Before we are reincarnated when we sit in the lap of the Goddess and we write our soul contract with her regarding all the things we want to learn and experience in our next life. We are beholden to that contract, and whatever is on that contract that we wrote ourselves is our fate, and yes, sometimes it "sucks". But everything else that happens in our lives is because of the choices we make and the choices made by others.
When I do a reading for you, and we are not doing a reading on your soul contract (unfortunately, 90% of the time Goddess does not allow me to discuss or delve into the soul contracts of others) , Then I am tapping into the Web of Wyrd which is a Norse Pagan concept meaning that all "fate/future" looks like a spider web, and at every juncture you can go left, right, forward or turn around. Sometimes when we find ourselves falling into the same patterns is because we are circling in the same section of the web.
And we are not the only ones on the web, so when I read for you I am reading what the most likely path you will take will be and that can be affected by those around you, because, what if your future life partner who for all intents and purposes should have gone right, went left instead. That messes with your timeline and your reading.
While this may seem like a bad thing or a reason not to get a reading, I believe that is erroneous. What a reading can do is give you clarity on a current situation (then we're not relying on multiple junctures in the web), a reading can be about your own spiritual journey and growth (these will always be the most accurate because we are only relying on you and your choices and not the choices of everyone else involved directly or indirectly in the situation.
This is also why timeline readings are one of the hardest thing to predict. I can do it, but there is always the chance that i'm slightly off because your crush may have suddenly been sent to Australia for 6 months for and since we didn't ask a question about that specifically it wouldn't have shown up in a reading.
Having free will in your reading is also a great thing because it means that if you get a negative reading and it seems like all hope is lost, there is always always always the chance that you can make things better. You can go to marriage counseling, you can finally sit down with your significant other and have that heart to heart, you can go to your doctor and see what other treatment options there are (as a side note, I very rarely agree to do medical readings since I am not a trained medical professional).
Your life has been in your hands since the beginning. Everything that is happening in your life now is due to you and everyone else around you fulfilling your soul contract .
I hope this answers some questions, if you find you have additional questions please ask them in the comments section below and I will try to elaborate.