Is a person who abstains from performing recommended acts of worship, such as "prostration of gratitude" and "supplication when rain falls," sinful if they suffer from social phobia and fear performing them in front of people?

What is a Sunnah (Prophetic tradition) or a Mustahabb (recommended act), such as supplicating upon rainfall or performing the prostration of gratitude (Sujud al-Shukr), is rewarded for the one who performs it, but the one who abstains from it is not punished. Thus, there is no sin in neglecting it. It is advised to strive diligently in seeking remedies to attain the rewards of these recommended acts and others.