Caught Between Desire and Logic

So I’ve been in an open relationship for about six months now. It’s not polyamorous in the strict sense because we don’t date other people per se, but we’re both free to have casual encounters if we choose to, as long as it doesn’t interfere with each other's emotional bond. My partner, Alex, is supportive of this arrangement, though they’ve always been wary of me stepping out of line, especially since I recently started working at a bar where the clientele is... let’s just say, more overtly sexual than most. One night, about three weeks ago, it happened. There was a guy there named Jake who came in often enough to know my name and always had a drink waiting for me when I walked through that door. He would smile every time our eyes met across the room, and after a few nights of this, we started talking more than just pleasantries. Tonight was different. We’d been flirting all night with little touches here and there, and it got to a point where neither of us could deny the electric charge between us anymore. He cornered me in the back room during my break, and before I knew what was happening, we were kissing intensely under dim lights. That’s when things got messy for me: one kiss turned into another, then another. Soon enough, Jake was pulling me closer against him with both hands on my waist, his erection clear through his jeans. I could feel the heat of his body, smell the alcohol mixed with cologne. It took everything in me not to give in fully to what felt like a magnetic pull. But then logic kicked in and reminded me why this was never supposed to happen outside of our open relationship agreement. If Alex found out about anything deeper developing between us here, it would end badly for everyone involved. I pulled back from Jake with reluctance but also determination, feeling the sweat on my palms as we made a silent agreement that what happened next couldn’t lead anywhere serious. So we decided to take things to the next level in one of the private rooms upstairs used for events and meetings. We were careful not to leave any evidence behind. It was exhilarating yet scary because I knew if this ever came out, it would break more than just hearts, it might shatter our entire relationship. The sex itself... well, let’s just say it pushed every boundary I thought existed between me and casual flings. There was an intensity to it that felt like a forbidden dance of desire we couldn’t deny even if both of us agreed afterward it had no future. So here's my question: Is there ever a time when the thrill of a spontaneous, intense encounter with someone outside your committed relationship can be justified? What lines should I not have crossed?