The Arabic word Sabr صبر implies many shades of meaning, which it is impossible to comprehend in one English word. It implies
1) patience in the sense of being thorough, not hasty;
2) patient perseverance, constancy, steadfastness, firmness of purpose;
3) sytematic as opposed to spasmodic or chance action;
4) a cheerful attitude of resignation and understanding in sorrow, defeat, or suffering, as opposed to murmuring or rebellion, but saved from mere passivity or listlessness, by the element of constancy or steadfastness. (2:45 Commentary)
An additional meaning implied in sabr is self-restraint. Haqqani defines in his tafseer as following Reason and restraining Fear, Anger and Desire. What can be a higher reward for patience, perseverance, self-restraint and constancy than that Allah should be with us? For this promise opens the door to every kind of spiritual well-being.
...Patient perseverance is ...active striving in the way of Truth, which is the way of Allah.
The Holy Qurán; meanings and commentary (IFTA)
Allah tells us in the 186th sign of the Chapter 'Family of Imran' that we shall certainly be tried and tested in our possessions and in ourselves. We shall certainly hear much that will grieve us from the People of the Book and the disbelievers. He further tells us that if we patiently persevere and guard ourselves against evil then it is from a matter of great resolution.
If we take a look at life in general we see so many things taking place all the time. Some phases of life pass by smoothly and we literally do not face any problem whatsover, like the phase of childhood for many. But even this phase is not all the same for everyone. For some even the innocent phase of childhood is not comfortable in every respect.
Later, other phases come in our life and we move on with growth, changes, challenges, ups and downs and loss and sorrow as well. If we analyse we can clearly see life as something that is not static for long...it keeps changing its shades and keeps giving us the taste of happiness and sorrow in big or small ways.
Nothing much is in the hands of man except the attitude he keeps during these phases of trials and tests in life. If he chooses to complain all the time he will only harm himself and in turn those surrounding him. If he chooses to take what is happening as a test and trial then he will choose to react wisely and avoid things that would harm his peace of mind.
One must understand that we can take action and change only that which we are in control of. No one is aware of the wisdom behind all the happenings in life except the One Who has given us this life, God Almighty.
Patience does not mean becoming passive and not showing any response, rather it means reacting and responding in the best manner which will not turn that calamity or trouble into a more serious one and we end up doing more damage than it initially brought.
Why patience and what actually will be called patience?
The answer to the first question can be as simple as 'why not' and 'what else if not patience.' If we give it a thought we will realize that being patient most of the times is the only wise solution to all the problems we face.
Suppose we take the simple example of children pestering you while you do some important task. What will you do if you choose not to be patient? You will end up shouting at the kids or beating them up or you will get overwhelmed and spoil the task you were doing. There can be many other ways to react without being patient and most of these will involve some unhealthy reaction at your part or will be harmful for the children. In this same situation if you react with patience you can firmly and politely tell them about the nature of your work and you would also provide them with something that will occupy them for a while as you work. There are many such situations occuring daily in our lives that demand our patience and self restraint.
This was a minor example. Suppose something really serious happens and it topples the whole scenario for someone. What is going to be his or her reaction? Obviously, most of us would get extremely shocked, hurt, sorrowful and also depressed.
The answer to the second part: 'Patience is often defined as your first reaction to the calamity'.
We as Muslims have been taught the ideal behaviour in all kinds of situations. There is a supplication for each situation and for such disastrous situations too we have been told to recite prayers.
Allah Almighty also teaches us in various parts of the Quran to be patient and that He is with those who show patience.
O ye who believe! Persevere in patience and constancy; vie in such perseverance; strengthen each other; and fear Allah; that ye may prosper.
There are numerous signs in the Quran that advise us to show patience, self restraint and restraint. The rewards of being patient are mentioned where Allah tells us that He is with those who are patient and He extends help to those who act patiently.
Patience is shown not just in calamities, disastrous situations or troubles but it is also a very important requirement for good realationships and harmony in the family and the society as a whole.
The topic of patience is very extensive and it will stretch too long if every aspect is taken into consideration. With a beautiful prayer from the Quran where the believers ask Allah to pour patience on them I will end this here:
"Our Lord, pour upon us patience and plant firmly our feet...