People are optimistic and we tend to overestimate how well things will go. We don’t understand how much energy and effort it will take to push through.
We like to assume things play out in a stable and linear fashion. It’s as simple as a straight line from here to there.
That’s never how it works and you need to work much harder than you think. It’s going to be far more difficult than either of us ever expected. If you’re not prepared for the effort required, you will fail.