Answer:
Muhammad Ali meant that winning is a mindset, not a skill set.
Step-by-step explanation:
Here he defined the mindset as a strong desire, a dream, a vision.
In order words, it is possible to have all the skillset required to be successful in an endeavor. If the person cannot see where he is going, he won't get there.
If he can see it but lacks the motivation to do the work required, he also won't get there.
He also mentioned that skill is important in the mix but that the will must be stronger than the skill.
In other words, will without skill is as useless as a skill without will. Both of them are two sides of the same coin.
A simple analogy would be someone who is hungry but has no money to eat, he'd be malnourished and famished. If he has money but simply cannot make up his mind on what to eat or where to get it, he'll equally end up malnourished.
Cheers