Way to go Usopp.
Here's what this made me hear in my mind as i was reading this
https://www.youtube.com/watch?v=4J7K3yacig4

Phil was waiting for ages. Good for him for taking charge of the situation.

Knee jerk reactions are what humans do, but our characters are smarter than us, usually.

Share a story about when a player did something on the spur of the moment, and then qualified it with some kind of previous set up to not make it seem so damn stupidly reactionary.

(Love the two "Arlong being shot" panels. Made me feel I was actually at the table when the temporary take back was done.)

Hmm... slight detour on this story time. Some game systems feature options to help impulsive (or not so bright) players portray a character who isn't so rash. For example, GURPS has "Common Sense".

The thing is some GMs basically give it out for free, or at least a selective version. I don't have a good specific version because "Are you sure you want to do that?" or something to that effect happened at least once per session. Just to make sure it wasn't too obvious, sometimes when we did something clever or at least more effective than the GM really wanted it to be, he (actually "hes" plural because I think every one of us did it while acting as the GM) would throw in "Are you sure?".

Plus we started doing it arbitrarily once we realized it was starting to get predictable as "Oh it is either really good or bad!".

The closest "On Topic" story is pretty simple; my first character took the GURPS Disadvantage "Pyromania". I mean I was in High School so indeed I was quite fond of fire, so it seemed like an easy role-play. Except of course just being "kind of fond" of fire isn't the same as being a pyromaniac. So as soon as it was brought up to me I started trying to role-play it; it still fit the character.

This resulted in me deciding to burn down a bunch of abandoned houses that were basically just sitting there slowly falling apart. I don't know if it was a miscommunication or what but at least one group member (the first of us to leave the group, barring some who only played a session or two) somehow got it into their heads that this was a serious mission. After some intense planning and what not this player (who was group leader at the time in-game) basically was all "Why are we doing this again?" and... I think the GM was tired of the adventure being side tracked as well. We either replaced the Disadvantage with one of similar value or I was allowed to buy it down to a Quirk Level ("Fascinated By Fire") so that we never had to waste that much time again.

But... Aren't our characters often also human? Just as prone to knee-jerk reactions?

Not so much justification, but....I was playing a Warhammer 40k game once, and I had a Felinid (Cat person) with extreme hatred of humans, and zealous faith in the God Emperor - it made sense in her backstroy - so when she was brought along with the rest of the team to rescue some people, and got wind that they were 'maybe' warp-tainted, she shot one in the face with her bolter before anyone else could react. It was funny. Nobody else thought so, because then we had to kill them all and failed the rescue mission, but I found it funny.

Oh dears. That moment when the player doesn't realize that what you're doing is put on for the benefit of stopping him from killing himself, so you have to go ahead and go through with killing him.

The best of times. The follow-up can be pretty educational, and sometimes even fun!

played a halflingy thief in a Star Wars based campaign.

had a flaw where charater loved shiny things and would hoard them like a pack rat.

helped party sneak on board an enemy space station, and killed some mercenaries in the hanger.
oh look one of them has a bandolier of Shiny Metal Orbs.

whoops, they thermal detonators.
BOOM.
all 6 went off. Dead.
Explosion was next to refueling station. Bigger Boom, TPK.
chain reaction that blows up the space station, killing everything including the campaign boss.

and that's why that flaw has been banned.

played a halflingy thief in a Star Wars based campaign.

had a flaw where charater loved shiny things and would hoard them like a pack rat.

helped party sneak on board an enemy space station, and killed some mercenaries in the hanger.
oh look one of them has a bandolier of Shiny Metal Orbs.

whoops, they thermal detonators.
BOOM.
all 6 went off. Dead.
Explosion was next to refueling station. Bigger Boom, TPK.
chain reaction that blows up the space station, killing everything including the campaign boss.

and that's why that flaw has been banned.

played a halflingy thief in a Star Wars based campaign.

had a flaw where charater loved shiny things and would hoard them like a pack rat.

helped party sneak on board an enemy space station, and killed some mercenaries in the hanger.
oh look one of them has a bandolier of Shiny Metal Orbs.

whoops, they thermal detonators.
BOOM.
all 6 went off. Dead.
Explosion was next to refueling station. Bigger Boom, TPK.
chain reaction that blows up the space station, killing everything including the campaign boss.

and that's why that flaw has been banned.

played a halflingy thief in a Star Wars based campaign.

had a flaw where charater loved shiny things and would hoard them like a pack rat.

helped party sneak on board an enemy space station, and killed some mercenaries in the hanger.
oh look one of them has a bandolier of Shiny Metal Orbs.

whoops, they thermal detonators.
BOOM.
all 6 went off. Dead.
Explosion was next to refueling station. Bigger Boom, TPK.
chain reaction that blows up the space station, killing everything including the campaign boss.

and that's why that flaw has been banned.

played a halflingy thief in a Star Wars based campaign.

had a flaw where charater loved shiny things and would hoard them like a pack rat.

helped party sneak on board an enemy space station, and killed some mercenaries in the hanger.
oh look one of them has a bandolier of Shiny Metal Orbs.

whoops, they thermal detonators.
BOOM.
all 6 went off. Dead.
Explosion was next to refueling station. Bigger Boom, TPK.
chain reaction that blows up the space station, killing everything including the campaign boss.

and that's why that flaw has been banned.