A believer who worships continuously may feel weary at some point. God, out of His mercy, knows that we humans could naturally feel weary, even in worship. Therefore, He diversified the acts of worship so that we can worship God in a variety of ways.
For example, prayer is a fixed act of worship that must be performed five times a day. But God recommended other forms of supererogatory prayers, such as the late-night prayer, the prayer of thankfulness, and prayer in times of need, and so forth. If the believer is weary from (optional) prayers, he may perform the obligatory prayers only, but at the same time, he may involve himself in other forms of worship, such as charity, performing umra, seeking knowledge, being kind to neighbours and relatives, helping people, and so forth. All these are forms of worship that draw one closer to God.