“being positive won't guarantee you will succeed, but being negative will guarantee that you won't.” what does it mean and why does it matter?

where exactly is the sentence

in the spreadsheet, click on a cell, then type the numbers or text you want and press enter or tab. to write data to a new line within a cell, press alt + enter. to enter the same data in several cells at the same time you must select the cells in which you want to enter the same data, in the active cell write the data and press ctrl + enter.