Depressing talks/managers

So I'm currently doing an SA at a MM and we're given a few talks by managers or just generally talking to people and something I see quite a bit is managers who try discourage you from the job or almost seem depressed about what they've done/are doing.

This isn't just because I'm at a MM either. I've been at other talks at BBs and I've had a similar experience. Many talk about how crap it is nowadays and how we're so unfortunate to be coming in at this time, or even just generally how it's not enjoyable.

Should I take anything from this? I've often heard that if you want to know if you could do your job for many years you look at your manager and see if parts of his life are what you'd want in yours. But having talked with a fair few who seem quite sad about it, is it just a test/them kidding around almost or what? As most I like to think I wouldn't be sucked in and do it for many years whilst hating it but these are all very clever and ambitious people as well.