The best way to become a writer is to write. They feel that every word has to lead to an end result rather than just allowing the ideas to flow. Some things you write you will want to discard. But you may discover flashes of brilliance in your work or ideas that you can use. No writing exercise is wasted even if it is only gets something off your chest.
Some writers keep journals or just scribble ideas in a notebook.
You might want to make observations about people eating in a restaurant or the particular way sunshine hits the waters of the lake. You just never know when these ideas might prove useful. If you create scenes or characters that you feel are unbelievable then likely these will not covince a reader. The best fiction comes from some inner truth or true experience that has happened to you. Sometimes fiction is an appropriate vehicle to vent emotions too difficult to otherwise share.