For me, history is one thing I base my speculation on. Take for example the halving, I know by history that bitcoin would get to a a new ATH by next year. Also, history makes me know that if certain events happen, it may affect the price of bitcoin negatively or positively. So I take the history of bitcoin seriously.
What I'm not good at is predicting the exact price of bitcoin at a certain time, but I know that after a while it would grow, that's why I prefer holding bitcoin for the long term alone.
I also use the current price of bitcoin to determine the future price of bitcoin. If bitcoin is at 20k today and saying it will get to 100l at the end of year is reaching. I like to be realistic when it comes to speculating bitcoin price.