Does a Muslim's feeling of joy or encouragement from others' praise for a good deed he has done invalidate the deed, even though his intention has not changed? Is this considered part of the "immediate good tidings for the believer"? And is constant fear of falling into hypocrisy and ostentation a form of obsessive-compulsive disorder, or a healthy state of faith?

If a servant acts sincerely for the sake of Allah, and people praise him, and he rejoices in Allah's bounty and mercy and is gladdened by it, then this joy does not harm him. This is indicated by the Hadith of Abu Dharr from the Prophet, peace and blessings be upon him: "That is the immediate good tidings for the believer." Constant fear of ostentation (riya') and hypocrisy (nifaq) and being cautious of them is a sign of goodness, as long as it does not lead to despair. The Salaf feared hypocrisy, and the Prophet, peace and blessings be upon him, warned his Ummah against the hidden shirk, which is when a man beautifies his prayer because he sees people looking at him. Al-Hasan Al-Basri swore that the believer fears hypocrisy, while the hypocrite feels secure from it.