Alongside working on the new Dungeons and Dragons Player's Handbook for the revised 5th edition of D&D next year -- yes, it's now referred to as "revised 5th edition," not "One D&D" or "6th Edition" or anything else --Wizards of the Coast is also working on revamping the Dungeon Master's Guide.
Some people are what's called eternal DMs -- they got into Dungeons and Dragons or other TTRPGs and started running games at some point, and it became almost all they ever do.
You really want to play a Halfling Barbarian, or a Warforged Druid, or for whatever reason, you rolled a character with no stats above 11 and you really want to play it despite it being utterly terrible at everything.
Not all Dungeon Masters will have the problem of having to wrap up a long-running campaign in a satisfying way.
One of the biggest pitfalls for novice game masters of any tabletop RPG is knowing how and when to say no to players.
Learning to improvise in Dungeons and Dragons: How to salvage a session when your players are Chaotic Neutral
Tabletop players are unpredictable -- that's what makes Dungeon Mastering fun, ultimately.
Being a Dungeon Master for a TTRPG like Dungeons and Dragons means a fair amount of work involved in running an adventure for a group of players, but you may be surprised how often that is all for nothing.
Everyone runs their game differently, and I don't mean to even try and tell you this is the way to be a game master/DM/whatever term you use for the person who runs the game here.
Nothing kills fun in a tabletop RPG faster than a rules argument.
Somebody having to step away from a recurring session of Dungeons and Dragons is something every party will have to contend with eventually.