". . . that reminds me of some advice I heard from Tracy Hickman. When walking up to the Dungeon and needing a Key (because the doors were just too darn massive to break through), throw up your hands and say "Well, that's it. We tried, let's go back to the inn." A poor DM will likely have the characters discover a key/secret entrance before the characters travel 50 yards."
Exactly the situation you don't want to be caught in as a DM. Equivalent to Toto pulling the curtain down and barking madly as you desperately turn wheels and flip switches. You've been caught out and the players know it.
Does it make you a 'bad' DM? If at all possible, I'd encourage the reader to avoid that notion as destructive. I don't mean to say that there aren't bad DMs in the world - but once you begin to self-identify yourself among their number, you're in trouble. Very soon after you will try to overcome your 'badness' by overcompensating in a dozen different ways - all of which will make your campaign worse, not better.
For example, the case above, where too much preparation demonstrates too much expectation from your players, who will be made uncomfortable by all the effort you're expending. You're thinking, "I just want to make a better game for the players," but what they're seeing is, "Wow, this is a big cage."
This tendency to overcompensate will emerge in various ways. You'll find yourself standing at the table, wildly waving your arms in the hope of increasing the excitement at the table, while in fact you're only causing others to withdraw. You'll be trying to make things bigger, like the speech the king makes to the party upon their success - but as the length of the king's address lengthens, the party will be searching for exits. You'll dig and dig for ideas that will be terrific, unique, profound, exciting, thrilling . . . but the party will sense your desperation and will not be impressed.
Then, after you've done all this work and you've totally failed - that failure now being thrown hard into your face - it will confirm that you are absolutely a bad DM, so that now you will feel the only thing you can do is quit. Having tried to be great, you've crashed and burned. It's a classic result.
See, there isn't any way for you to force yourself into being a better DM. The more you try to force the issue, the tougher it is going to get and the more you're going to be hiding behind a curtain that will fail to cover for you. There's only one way to be a better DM than you are - and it is the hardest thing imaginable.
You have to wait for it.
Everyone starts as a bad DM. Not everyone realizes it; there are plenty of DMs out there who have smoke blown up their ass every day by players who have never played anywhere else - or who have played with even worse DMs. Everyone, however, started bad.
By 'start,' I mean you're in your first three years. That seems really unfair. Chances are, if you've been DMing for three years you probably feel not to bad about your abilities; you've already outlasted most of your friends - lasting longer than your friends thought you would - and mostly you get a lot of praise for your games. Players want you to keep DMing and that even if you secretly doubt your ability . . . there are going to be a lot of sessions you build the courage to run by reminding yourself that the players like you.
It seems doubly unfair that you're being told this by someone older with tons of experience who must be either superior or conceited. What do I know of your game, right? It's easy for me to say that everyone in their first three years is a bad DM when I'm comfortably way past that.
Yet I can be draconian about those three years because I know that 'good' only comes with practice. You may be great right out of the gate, but even to you that is going to seem like shit once you've practiced and developed some perspective.
It isn't enough, however, just to keep doing the same thing over and over for years at a time. That only ingrains the badness. Practice implies the adaption of new things, to be able to do something next year that you cannot do right now. And this takes time.
That is why the push to make your world better by gimmicking it up with cool traps and elaborate rooms and exciting storylines or characters is a dead failure. Implementing any of those things well takes practice. You have to acquire those skills steadily, painstakingly, incorporating them not just into your repetoire but into yourself. You have to adjust your play session-to-session to actually be the wizard, without the curtain and without the pretend giant head.
This you cannot do if you're wrapped up emotionally in how bad you are. This you cannot do if you're concerned about how long it is going to take or if you need approval throughout the process to keep going forward.
If you want to be a good DM, you're going to have to stick with it, in both good times and bad. You're going to have to run tough parties, you're going to have to skill-up where it comes to keeping the table from getting out of control. You're going to have to suffer. Most of all, you're going to have to NOT QUIT.
I look around at people I am associated with in a variety of efforts - musicians, painters, film-makers, artisans, photographers, puppeteers, actors, performance artists, writers, designers, clowns, promoters, cavers - and I see a lot of people with tremendous skills and varied success. Most of us, together, are experiencing some notariety. We make fair money through the year, not enough to live on but fair, we produce new work, we struggle with our individual strategies to get attention and improve ourselves. We get together for coffee and describe to one another what's working and what hasn't, what we gave up on, what we're manoeuvring ourselves to try next - and we encourage one another mostly to keep working. We're all still in our fields after several decades not because we've hit success - those who have hit it have moved on, out of our social circle - but because we all recognize that quitting is impossible. We've all known quitters, dozens and dozens of them; people we went to school with, people we performed with, people who claimed commitment or sacrificed their relationships for success, who burned themselves out in the process of seeking, who toured, who made themselves broke, who bought themselves expensive instruments or poured money into equipment and film, who lived for it and paid as much as any of us today have. Only, in the end, they quit.
I'll add dungeon master to the above list, because it belongs. It costs, it burns people down, it demands commitment and it is just as unforgiving and unyielding as any other art. We apply ourselves to it, we experiment and investigate and change ourselves because of it. And we get good by doing it, doing it, doing it. If it isn't working, there's nothing that will solve that problem except doing it more. It doesn't help to get excited or to get into a funk. Gotta wash the emotion out of it, because that's what washes out the doubt. Eventually, comes the certainty that yes, we know how to do this thing - because it has stopped being about patting ourselves on the back. Now it is as incidental as breathing.
Stay with it. You'll see what I mean.