Mistakes will be made by the way. Some mistakes will be made along the way. That’s good good because at least some decisions being made along the way. We will find the mistakes and we’ll fix them.
The road to success is paved with mistakes well handled.
An expert is a person who has found out by his own painful experience all the mistakes that one can make in a very narrow field.
[Though more popular, it is commonly shortened to: "An expert is a person who has made all the mistakes that can be made in a very narrow field."]