re: 'you can't do it'.
Disagree: first, anyone making a trade IS predicting the future, they have predicted that the price will move in the direction of their trade, otherwise they'd have no trade to make.
" the only thing that exists is now, and the past." the 'past' exists ???
Your " ... dirty laundry ..." exists in the present only until it's washed, then it exists in the past as your memory of its existence.
There are people who can predict the future, particularly those who have psychic ability or pronounced intuition if you prefer, and there are many simple daily examples that such 'uncanny' experiences are a part of virtually everyones life experience.
Certainly price targets are easily predicted with the fibonacci ratio, tho time is more difficult to target precisely.
We don't re-experience the past except by recall, we certainly don't live in it and it does not therefore exist in those terms, likewise we do not live in the future, but the infinitely small separation between past, present and future is difficult to discern.
The most practised at truly living in the present are usually practionioners of meditation in its various forms, or when the 'rest of us' are pushed to critical/overload when we focus exactly on the immediately important, being struck by a loosing trade perhaps.
Prediction of the future whether or not based upon the past and whether or not an opinion is still prediction, without it our thinking would be locked in the past, we could not think what to do next.