He is Lord of the heavens and the earth and everything in between them, so worship Him and persevere in His worship. Do you know of any other with His Name? (Surah Maryam; 65)
"To be resolute" is to be firm in purpose and persistent therein. Allah orders Muslims not only to perform acts of worship, but also to be resolute in performing them.
However, some people tend to limit the concept of being resolute in worship to certain obligatory acts such as regular prayer, giving alms, fasting or pilgrimage. In its true sense, however, worship means "being a servant." That is, a man's attitudes, behaviors and whatever he does to serve Allah are all acts of worship. Compliance with what is ordered in the Qur'an comprises many important obligatory acts of worship, and is in itself an act of worship.
Controlling one's temper, speaking gently and kindly, warning people of the Hereafter, avoiding wicked thoughts, and refraining from pointless dispute are all acts of worship. Therefore, this commandment refers to both the physical acts of worship and the moral excellence that a believer adopts for himself.
Yet, the resoluteness of Muslims will be put to test. Stories of prophets and believers of the past portray events by which their perseverance was tested. Trying times are shown to be invaluable opportunities to demonstrate a Muslim's loyalty to Allah.
The verbal and physical attacks of unbelievers are among the occurrences through which a Muslim's loyalty to his religion is tested. Disease, thirst, starvation, exhaustion, threats and life-endangering situations are also tests for believers. There will be many times when a Muslim must persevere to live by the principles of Islam.
There are also times when Allah grants to believers such favors as health, strength, wealth or power. These too are invaluable opportunities through which they can demonstrate their commitment to the religion of Allah. That is, Muslims will be tested with both hardship and ease, yet neither should make them deviate from righteous conduct.