I've been in a couple of abusive relationships before that have taken their emotional toll (occasional nightmares or a random trigger). I also suffer from seasonal depression that can get pretty sticky. I've worked really hard not to feel like these things make me less deserving of a warm, loving relationship. Though those thoughts creep in occasionally.
When do I tell this guy that I might feel unglued once in a while? How long is acceptable to hide it? Right now I go home or take a night off from him if I feel like it's going to be rough mood-wise. But I sense that someone must have an answer on how to be transparent about mental health without having it ruin a relationship.
Anonymous: If having very (very!) normal needs and frailties is a relationship killer for this guy, then it will be a relationship killer whether you say so now or two years from now. And better to find that out now, no?
Or worse, he notices stuff because that's inevitable, and you don't explain anything because you think you'll lose him, and he finds out two years in and your withholding information from him is what kills the relationship.
Please treat your needs as matter-of-fact: Say when you need a night off for mood management. Say why. Mention the seasonal depression. When old relationships come up, say that you've had some bad enough that you still get nightmares sometimes. Having various health problems is common; the ability to anticipate trouble and head it off is not common, and in fact it speaks well of you.
You need, as a partner, someone who can see that, which is another argument for finding out whether he can (sorry) handle the truth.
Of course, you don't want to unspool your entire self on first dates; there is a pace of disclosure that makes sense. But it's not about some perceived line before which you hold it all in and past which you dump it all out. It's about trust and investment.
When you first meet someone, unless you're train-strangers having a mutual no-strings-attached catharsis moment, it's reasonable to believe the other person cares only so much about your every life detail, and will be only so responsible about respecting your privacy. So you share to a degree, roughly, that reflects basic respect for the level of detail that would interest someone new. Gauge interest from questions, read body language, think candor and brevity.
Then follow this give-and-take path accordingly as you get to know each other. One little nudge closer at a time, as you feel safe to share about you and curious to know about him. Watch for natural openings to bring up difficult things.
If you're not sure where you are in this progression, consider: When not telling feels like "hiding," it's time to tell. There's your opener, too. "I should have said this sooner."