I am 2.5 years into my career and I burned out at the 18-month mark. The thing is, I didn't know it was burnout. I thought that's just what the job was. Everyone around me seemed to operate the same way. Slack after 10pm, weekend Slack, 'quick syncs' that were a full hour, being online during PTO. I normalized it completely.
Early-career burnout has a specific texture. You don't have enough experience to know what normal looks like. You're still trying to prove yourself so any sign of flagging performance feels like proof you're not cut out for this. You're also in a phase where grinding hard has always worked, in school, in internships, so you just keep turning the intensity up because it worked before.
For me the signal was crying before logging on. Not sometimes. Regularly. I told myself it was just a rough quarter. The rough quarter lasted 6 months.
When I finally said something to my manager, the response was actually decent. They hadn't realized how underwater I'd been because I'd been hitting deadlines. My outputs looked fine. The cost wasn't visible anywhere except to me.
A few things I'd tell my earlier self:
Being new doesn't mean being available constantly. It can feel that way because you're insecure about your standing, but 24/7 availability is not a job requirement anywhere legitimate.
The 'this is how all tech jobs are' belief is often wrong. Varies a lot by company, team, manager. You don't have enough data points yet to know if you're in an outlier situation.
There's a difference between being challenged and being depleted. Both feel hard, but challenge usually has some energy underneath it. Depletion doesn't.
I'm in a better situation now. Same company, different team, different manager. It's not magic but it's noticeably different. Raises for me were a lot more about finding the right micro-environment within tech than getting out of tech entirely.