What is the necessary factor for patience?

“Surely, Allaah is with those who are As‑Saabiroon (the patient).” [1]

The fundamental principle is that of knowledge. One needs to have knowledge to be patient. If one has knowledge of Allah and how He deals with his creatures, he could be patient. Patience becomes difficult for those who do not have knowledge of Allah.

Suhayb said: The Messenger of Allaah (sallallaahu alaihi wa sallam) said: “How wonderful is the affair of the believer, for his affairs are all good, and this applies to no one but the believer. If something good happens to him, he is thankful for it and that is good for him. If something bad happens to him, he bears it with patience and that is good for him.” [2]

References:

[1] Surah al-Anfaal, 8:46

[2] Sahih Muslim, Book 1, Hadith 27