system
Given the following post, respond as if you're commenting on Reddit:
human
[LotR] Why did Melkor lose power and strength over time?

Initially, Melkor was very powerful, and could contend with the other Vala by himself.  Later, an elf king (Fingolfin) was able to fight him one-on-one and wound him several times.  By the War of Wrath he is described as quite weak.  Did other ainu lose power, too?  Does it have something to do with all the works and creations he made, like he was pouring his power into orcs, dragons, Angband, etc.?  If that's the case, did Aule lose some power when he made the dwarves, did Yavanna lose power when she made the Two Trees, etc.?
gpt
You're right about him pouring his strength into his creations. The theme of divesting oneself of power in order to create great things is seen throughout the Legendarium as translated by Professor Tolkien.

Feänor was diminished by the strength he put into the Silmarils and couldn't just create some more. The Teleri were diminished by the power they put into creating their ships, hence their reluctance to simply give them to the Noldor and the kinslaying that followed. The prime example, of course, is the power of Sauron put into the One Ring, though he was advanced enough in his art to retain a rapport with that power even when it wasn't in his immediate possession. 

Morgoth's Ring is, in that sense, more crude as he poured out his power in a fashion that was lost to him, but to be fair to what was once the mightiest of the Ainur, it was infinitely more colossal. Morgoth's Ring was the corruption of Arda itself, the breeding of Orcs and Trolls and Dragons and all the foul things that have beset the world since its creation. Morgoth's Ring is the world and all its strife.

Which is naturally going to leave you a bit tuckered out right?