What makes it worth it to you?

Some background about me. I'm currently interning in asset management, but I have always loved M&A. I like doing valuations and I like looking analytically at companies to see what is of importance to a specific client. I always excelled at doing case days whenever I attended career events at local banks and boutiques in my country. I used to see the long hours of M&A as just something I'd push myself through because I liked what I would be spending my time now. But now that I have a nice job that requires me to work nine to five, that is starting to look a whole lot less appealing. Here its common for IB jobs to require 60-70 hour workweeks (so nothing compared to what you'd see on wallstreet or even london). But I'll tell you, hearing an associate brag about being able to sometimes leave work at 5pm on a friday when you finish work at that time every day, its jarring. Do you just have to love your work that much? I thought I did, I'm so not sure anymore.