Of late when analyzing why I am dissatisfied with the sessions I've been running, I've come to the same conclusion: I'm rushing myself. This makes sense to me. So much GM advice - even the advice I give - is to mind how long things take. Pacing is very important to a game. Delays in getting things done can cost a player's attention, and thus lose a huge chunk of enjoyment for the game. It is important to keep things moving, to keep the ball rolling as they say.
But there is a difference between keeping things going and the pace up, and skipping meaningful content or additions because you feel like you don't have time.
Barring extenuating circumstances - like a player leaving the area and thus unable to stay in the game - there is no reason to have to rush. There is no rule saying your campaign can only be 26 episodes for a 'season' of TV. There is no rule saying your session can't go a few minutes over when important to do so. There is no rule saying you can't split your plan for one session into the plan for two or even three sessions.
More to the point, descriptions, quips, and dialogue that gives insight to the characters, setting, or plot going on is meaningful for the game. Having time and effort put in to some proper descriptions and dialogue is the difference between Strahd and Generic Vampire #8291. If you want your players to enjoy your villains, there has to be time for the villains to show why they're worth enjoying. If you want your players to develop their characters, you have to challenge the characters and give time for them to respond and grow.
Breathe. Forget the clock. If you want your game to have fun stories and meaningful character moments, then make time for those moments. You're not wasting time by doing that. You're not stalling by doing that. You're giving time to the things you want in your game.
And that's just good GMing.