What honestly surprised you most when you ran (or played in) your first full campaign?

I’ve been talking to a lot of indie TTRPG creators lately — people designing their own systems, running campaigns, preparing Kickstarters — and one thing keeps coming up: the gap between what you planned and what actually happened at the table.

For some it’s pacing (sessions ran 2x longer than expected). For others it’s player attachment to NPCs they thought were throwaways. For some it’s the opposite — a carefully built villain got ignored completely.

As someone who builds tools for TTRPG creators, I’m genuinely curious what the community thinks:

What’s the one thing you wish someone had warned you about before running your first campaign?

Could be prep, could be player dynamics, could be the mechanics themselves. No wrong answers — I’m here to learn from people who’ve actually been at the table.