First...I will agree with you that we all have the possebillity to shape our destiny...and with postetive thinking and "stayer will" you can come far!
I belive it's dumb to make statement like our destiny are made for us...that is just a sleeping pillow.
When it comes to Tarot and Tarot readings, we are again talking about belief.
If you believe that Tarot can give messages and predict future, then this messages has to come frome some place.
Some readers are good and have a very good intuation, they can predict with great accuratcy without even know the quarrant.
Is't the reader or is't the cards that gives the message?
Since each card have a "basic" meaning, I think the cards tells and the reader "translate" it.
In order to tell something that have great accuracy, time after time, you can't believe in luck that the right card's come up for the right time.
So...yes....if you believe in Tarot....then you must also believe that the messages come from "spirit world" true the reader.
If you can accsept this, then the spread itself is the most important part of the reading. With this I think of the translating. We all translate it our own way and from different angles, so if you want a second opinion on a spread...don't make a new one...but let another reader translate it
I have also read that Tarot back in the old ages was used as a learning and inspiration tool for common people.
This will then be used the same way as you do now...and other do...put up some cards and give the people posetive impulses in order to improve their life quality.