o que significa a expressão walk a tightrope?

I was engaged in some reading this afternoon when I came across an expression in a tribute to Paulo Freire, who by the way was the topic for my classes this week. 

Among many other things, the tribute describes part of his pedagogy which consists of making people assume their responsibilities, make decisions without outside interference and finally "to walk the tightrope between shade and light,..." 

When you walk a tightrope, you do something that requires extreme care and precision in a situation that allows very little or no error. A more practical way of understanding the expression would be to imagine yourself dealing with problems that are far beyond your control or difficult to solve, such as layoff at work, failing business, finantial management, etc. You're so stressed out about the consequences or the outcome of your decisions and behavior you feel like you're walking a tightrope. And if you haven't figured out what the expression means in a literal way, just check out the picture below. That woman is waking a tightrope.