What is the fine line between confidence and arrogance?

Is there truely a line, where one can say, that I can be confidant in what I do and say because I know that I am right, but yet no way possible be labelled as arrogant in some fashion?

When attempting to continue through, motivation and drive to complete something instead of straight abandonment when a "better" opportunity arises, there must be a justification to not leave the current situation. But to generate the motivation, the confidance that you know you are doing something worthwhile has to be there.

But if it is called arrogance, where does the confidance go? Is it no longer worthwhile? Perhaps so the "better" oppotunity is the way to go.....

A simple line, a device of words to display confidence.
"Although these areas of work are useful in progressing the understanding of spray drying applications and the ongoing expansion of spray drying use, nothing in particular is revolutionary and there is no leap required for new innovation in this field".
The confidance to say that, to know that something is true.

But does this work lose meaning, and the tumble of motivation if it is considered arrogant to make such a bold statement?

In the end, all it requires is one person to make that claim, that in the eyes of others, it may not be revolutionary. A quick deflation ensues.