Is it obligatory to conceal good things that are expected or that occur, for fear of losing them, based on the saying, "Seek help in achieving your affairs by concealing them," or could the reason be envy?

There is no definitive reason for what was mentioned, but it is legislated for a Muslim to conceal matters from which he fears envy or harm, as Ya'qub did with Yusuf (peace be upon them both) when he commanded him to conceal his vision from his brothers. Likewise, concealment is sought for the fulfillment of needs, as the Prophet (peace be upon him) said: "Seek help in fulfilling your needs through concealment, for every possessor of a blessing is envied." However, if one does not fear harm, it is good to speak of blessings in gratitude to Allah without boasting, as Allah Almighty says: "But as for the favor of your Lord, report [it]."