Let us start from the end. Let us start with the answer.
Question: how do you know it is time to leave?
Answer: you do not know. It is possible you never will.
What is broken about modern sign-reading is the foolish wait for an answer.
What is more broken about it is the thought that the answer is supposed to be revealed to you, if only you sit quietly and look at the sky. Or at the internet.
And nevertheless.
A great many of the important changes in our lives involve a separation or a departure. To be direct about it, that usually means leaving a job or a romantic partner.
So I am going to give you my two pennies, but I warn you not to respect what I write too much. I have made too many idiotic decisions in my life and missed too many things that passed under my radar, which makes me the most redundant guru available. Consider yourself warned.
Here are my thoughts on leaving.
One. Before anything else — the level of personal distress.
Not every continuing difficulty warrants a commission of enquiry. And yet, if the standard condition at work or in love is suffering, consider ending the contract.
Suffering is necessary if it makes you undergo a process from which you emerge better. The pains of a diet, or the growing pains of a business.
Suffering that produces nothing is simply damage, and the fact that you can withstand it is not an argument for continuing to.
Two. Ask what you are actually waiting for, and whether it could arrive.
Most people who stay too long are not waiting for a decision. They are waiting for permission — a sufficiently terrible event that would justify leaving to an imagined jury. Which means they are quietly hoping for something bad to happen, and will keep waiting until it does.
Three. Notice the difference between wanting them to change and wanting them to have changed. The second is nostalgia, and no future action can satisfy it.
Four. You will not be certain. Decide anyway, and accept that you are deciding under uncertainty, because the alternative is that the decision gets made for you by the passage of years.