The simplest right of yours.
What was then - had gone.
What will come - we'll never know.
What is now - is all we have.
And all we need is use it well.
Let's imagine a few situations that in some cases can change a lot.
Even if you are a plumber, you can be useful besides your primary purpose. What if one day, while mending a tap, you accidentally hear phone conversation, that your client cheats its own spouse. Would you tell about this, if you could? If no, you can always remember, that he or she works at the Nuclear power plant, located nearby. I guess you don't wont the workers to be inattentive at such job.
It was so called light case. But imagine, you've been inventing cure from death for ten years now. What would you think? I mean, the closer you to achieve it, the more pressure you'll feel. Responsibility for your actions can only be taken by you, and because of that you can go mad. There is not just one person, but whole mankind who depends on you.
And it doesn't matter who you are, a plumber or a scientist. It depends on you what to choose.