﴿ لَقَدْ نَصَرَكُمُ ٱللَّهُ فِى مَوَاطِنَ كَثِيرَةٍۢ ۙ وَيَوْمَ حُنَيْنٍ ۙ إِذْ أَعْجَبَتْكُمْ كَثْرَتُكُمْ فَلَمْ تُغْنِ عَنكُمْ شَيْـًۭٔا وَضَاقَتْ عَلَيْكُمُ ٱلْأَرْضُ بِمَا رَحُبَتْ ثُمَّ وَلَّيْتُم مُّدْبِرِينَ ﴾

“Indeed, God has succoured you on many battlefields, [when you were few;] and [He did so, too,] on the Day of Hunayn, when you took pride in your great numbers and they proved of no avail whatever to you -for the earth, despite all its vastness, became [too] narrow for you and you turned back, retreating:”

Reliance on oneself develops sort of a haughtiness in a man which results in carelessness of external facts. He falls short in carrying out disciplinary regulations. Due to overweening self-confidence, he starts acting in an unrealistic manner, the result of which is necessarily defeat in this world of cause and effect. As opposed to this, having confidence in God is reliance on the greatest power. This develops humility in a man; he becomes extremely realistic; and realism is the key to all success.