Suppose you are an A-Level student. You desire to be a university student.
You should know that
(1997 – 1999; study hard) (1999 – 2002; university student)
In 1997, I wanted to be a university student. I could not transform myself to be a university student immediately. I could not travel to 1999, becoming a university student at once. However, I knew that, ideally, if I worked hard (and worked smartly) now (1997), I would be able to enter university. In other words, the event “being a university student in 1999” is equivalent to the event “studying hard in 1997”.
I could not control an event in 1999 as it was in my future. But I could control the present-equivalence of that future event.