Lost My Head While He Wasn't Looking

I recently broke up with my partner of five years. It was mutual, but I've been feeling a bit aimless at work and struggling to maintain the same level of productivity as before. Last week, I ran into an old acquaintance from college, Jack, who had always sparked something in me that I couldn't quite define back then. We hit it off over coffee, catching up on old times and reminiscing about our younger years together. As we parted ways, there was this electric feeling between us. A few days later, after a particularly tough day at work, I found myself messaging him again. Our conversation turned flirtatious quickly, leading to some playful sexting that escalated into plans for a lunch date outside of work hours. The next day, we met up and things got heated in his car. We kissed fervently, my hands exploring parts of him I hadn't revisited since college. It felt freeing but also guilt-ridden. Why did I seek this out when I was still grieving the end of a relationship? Is it because Jack represents a chapter of my life that feels more carefree and wild than where I am now? Do I just need a reminder of what it’s like to feel desired by someone new, or is there something deeper at play here? Am I being selfish in trying to rekindle feelings from years ago while the dust settles on another relationship's end? Your thoughts?