according to an article I read, is when we can meet each moment of life as it is, not as we would have it be, and respond to it skillfully.
Can - that is the difficult word - the difficult part.
Who wants unhappiness, and unpleasantness? who wants sorrow and grief? who wants loneliness and despair? For many, this is what each moment is.
Responding skilfully - I've found that very often silence is the best response - but with a very important rider - YOU COME FIRST. So, in the silence, first attend to yourself. It is better not to say things one would regret in retrospect, and more importantly, by keeping quiet the situation does not escalate into something we won't be able to handle at all.
The article has words of hope: People who practice mindfulness (meeting each moment) will tell you that they get better at enduring pain, better at solving problems, better at not creating misery for themselves, and better at participating fully in those moments of life that are joyful.
Worth a try....?