What happens to a lot of people is that they enter into a new endeavor full of energy, basically bursting at the seams, barely able to contain their excitement. They see endless horizons and opportunity, not at all worried about the challenges they will face.
You could compare these people to shooting stars. They burn brightly and brilliantly across the sky but their time is fleeting; before long they burn out. Although it might sound counterintuitive, tempering expectations from the get go might be the best way to achieve your goals. You become aware that if you want to stay in it for the long haul you’ll have to take off those rose colored glasses, preparing yourself for many obstacles along the way.
In our astronomy metaphor, you want to make yourself a satellite, plodding steadily and purposefully across the night sky, not a shooting star, which might look prettier and brighter but also has a much shorter shelf life. Preparing for setbacks from the beginning makes you more resilient, less likely to give up when these setbacks come along since you were expecting them from the start.