One has various things in the back of one's mind. Occasionally an opportunity presents itself to bring one forward. Most of these opportunities come to nothing. Once in a very great while one -- or two -- do come to something.
The quote reflects on the idea that people often have numerous thoughts and ideas in their minds, waiting for a chance to be expressed or acted upon. However, most times, when opportunities arise to realize these thoughts, they don't lead to significant outcomes. It highlights the uncertainty of whether an idea will resonate or succeed when finally given a chance.
Nevertheless, the author suggests that occasionally, a rare opportunity does lead to meaningful results. This notion emphasizes the importance of perseverance and the readiness to seize moments when they arise, illustrating that while most pursuits may not bear fruit, some can truly flourish and make an impact.