Shaytan will try to blind us from reality. He will make us forget that victory is from Allah alone by making us feel inferior, and using other people to make us think our goals are unattainable. Well, we must remember that all things are decided by Allah alone. Trust and reliance should be on Allah. Allah says:
“If Allah helps you, none can overcome you; and if He forsakes you, who is there after Him that can help you? And in Allah (Alone) let believers put their trust.” The Noble Quran in The English Language 3:160
Tafseer Sad'i says,
That is, if Allah sends to you His support and help, {none can overcome you}, even if they gather against you all the people of earth, with all their numbers and weapons, because no one can overcome Allah; He has subjugated all people and has taken hold of their forelocks, so no living being moves or stands still except by His leave.
{If He fosakes you} and leaves you yo your own devices {who is there, after that, who can help you?} You will inevitably be defeated, even if people help you. In this there is an implicit command to seek the help of Allah and rely on Him, and to admit that you have no strength and power of your own. Hence Allah says: {In Allah, then, let the believers put their trust}.
The fact that Allah is mentioned at the beginning of this phrase indicates that they should put their trust in Him alone and in no one else, because it is known that he is the only supporter, so rely on Him is indicative of belief in His oneness which will help you reach your goal, whereas putting your trust in anything else is a kind of associating others with Him which is of no benefit at all, rather it is hamful.
In this verse is a command to put one's trust in Allah alone, and the level of trust will be commensurate with the level of the individual's faith. (see Tafsir as-Sa'di Juz 4-6 Page 81 Published by IIPH)
