Consistency between “yes and” with “no, because I’m the DM”

Context: I enjoy running softer systems, with Numenera being my latest favorite. I discard rules left and right in favor of what feels right during the play. I love the "rule of cool" too, and I use it liberally.

One of my players is rather creative and often vividly imagines the outcome of their plans. How do I help them manage their expectations when these plans can not come to fruition for DM reasons?

It’s easier to explain this with examples. Here’s an example of me letting the player have fun with their creative solution:

  • DM: The bad guy is monologuing safely behind a force field.
  • Player: I use my cypher of bypassing force field and my superhuman speed pill I swallowed 3 hours ago (and they indeed have) to tackle the bad guy.
  • DM: Give me a roll.
  • Player: 20.
  • DM: You succeed.

The rest of the players jump in to restrain the baddie, everyone celebrates and players have fun. I’ll survive not having a bigger showdown here.

And here’s example of me not letting the player to go forward with their plan (all the rolls are 20s in this example to double down on the problem — I gave the player opportunity to roll, they critically succeeded, but I don’t want them to):

  • DM: The bad guy is leading you to his office.
  • Player: I "accidentally" tap the bad guy on the back to make sure they’re not a hologram.
  • DM: They’re not.
  • Player: I’m walking last, and I put on my invisibility cloak.
  • DM: Give a roll.
  • Player: 20.
  • DM: You succeed.
  • Player: I sneak behind him and slice his throat while he talks (this seems like a murder-hobo response, but the character had a solid motivation behind this)
  • DM: Give me a roll.
  • Player: 20.
  • DM (trying to save a recurring villain for a larger ark): You attempt to do so, but in the last moment the bad guy wiggles out and yells for guards. A fight ensues.

Villain activates a mysterious device and teleports away during a fight. Also, since this is a Numenera game, I give out my players some experience for the GM intrusion and out of some guilt.

How do I manage players expectations without discouraging them from finding creative solutions to problems presented during the game?