Sabr (patience) comes from a root word meaning to detain, refrain, and stop. Applying this to our lives as Muslims, it means to stop ourselves from despairing and panicking and to stop our tongues from complaining. O Slave of Allah! Why do you despair when you know your Lord is the Most Merciful? Why do you panic when you know Allah is your Protector?
O Slave of Allah! Why do you complain to the people, when your Lord is All-Hearing and is able to do all things? O Slave of Ar-Rahman! Be like

Yaqub alayhi salam when he said:
He said: “I only complain of my grief and sorrow to Allah, and I know from Allah that which you know not.” [Surah Yusuf V.86]

Or be like Musa alayhi salam who prayed to Allah azza wa jal saying:
“O Allah! All praise is due to You, and complaint is made only to You, and You are the only One from whom we seek help and in whom we put our trust, and there is no power except by Your help”

Or be like our beloved Prophet sallalahu alayhi wasalam:
“O Allah! I complain to You of my weakness and helplessness”

These were the greatest of people that ever stepped foot on this earth and they were a people who only complained to the Lord of all the worlds. Why? Because complaining to Allah is of great benefit while complaining to people is of no benefit. Complaining to Allah is a form of true patience, worship, and great reward while complaining to the people is Gheebah/ backbiting.