The literal meaning of these words is
“To change the situation (adverse),
Is not in our hands,
But to change our thoughts arising out of the situation
Is in our hands”.
Therefore it is not the situation however tough it may be that makes us unhappy and disturbed, but it is thinking about that situation that disturbs our mind. In fact if we do not react to the situation we can approach the problem with a cool mind and resolve it.
E.g. If an executive is sacked by the corporate HQ and it takes two days for the orders to reach him. For those two days even though the situation had occurred his mind continued to be at peace. But the moment he got the news he was in a state of misery and fear due to all the negative thoughts concerning his dismissal. Yet if he would accept the situation (as it had already occurred) with calm he could start searching for a new job quickly and efficiently.
It is said that “He who does not allow his thoughts to over power his mind, then no power on earth can ever disturb him”.