How can I remain steadfast and consistent in acts of worship, such as reading the Qur'an, performing tasbeeh, and fasting, especially since I start with enthusiasm but then discontinue after a few days?

The human soul experiences periods of receptiveness and aversion, of activity and lassitude. When it is inclined towards acts of obedience and supererogatory prayers, engage in them without excess or deficiency. And when it turns away, do not burden it with what it cannot bear, while always maintaining the performance of obligatory duties.