How do you become a better GM?
Become one with the system.
Some people think the GM is a player, just of a different kind than the other players. This is not true. Certainly as a human being with her own sensibilities, the GM experiences many of the same subjective delights that the players do, and gets to be an audience for them just as they are for her. But the GM is not portraying or identifying with a person who faces obstacles in order to attain successes. It would be pointless to do so, because of the tremendous power she wields relative to the players.
Even in games where the stated object is for the player characters to get creamed, go insane, or otherwise "fail", that in-character failure is an OOC player success, exactly because it was a stated object of the game. The GM's successes, on the other hand, are all OOC. Even when enacted through an NPC. They are successes of artistic performance, and they happen in the real world.
To put it another way: If you actually do want your NPCs to succeed and your players not to, you're doing it wrong. In fact, you're an asshole and you shouldn't be trusted with the contents of other people's imaginations.
The GM is not playing a game. The GM is, in fact, part of the game's system. She is the part that cannot yet be automated.
The function of the GM - whether performed by a single person or distributed throughout the group - is to adjudicate all aspects of uncertainty and convey all aspects of existence within the gameworld (including color, atmosphere and the behavior of NPCs) which cannot be handled by the rules and mechanics at the level of detail, verisimilitude and originality demanded by the aesthetic expectations of a modern audience vis-a-vis a given genre and story type. The GM is like a delivery platform: that part of the system which helps the players jump the gap from Projection to Immersion.
Even in PbtA games, where the MC has "moves" and rules that control when they may be made; even though the MC decides which of those moves to apply at any given time, her every utterance is guided by the "Always Say" rules, which command her to always say "what the rules demand" and "what honesty demands". This is a directive to remove ego from the equation. This is an injunction to become one with the system.