Ask yourself if you're ready to stop (more important than it seems)
Understand crying is a natural function of the body, crying constantly for days on end should something of a warning light
If you haven't already, it might be helpful to find a safe, isolated location
Focus all attention on a noise in the environment (helps to bring you "here", quiet mind noise)
Attempt to physically calm through "box breathing", 4 in 4 out 4 hold. This can also minimize panic attacks
The words we say and thoughts we think can have power over us, in that we use them to make connections to meaning. Try to refute any thoughts that are obviously out of line, so you don't wind up convincing yourself you agree with them. For me, that's as simple as saying "refute" in my head.
If you live with loved ones, it's a really good idea to let them know what's up. This minimizes their potential distress at discovering you and establishes a route for support, if necessary.
If the breathing and focus has succeeded in bringing the crying to a halt, I try to return my expression to a more normal one and relax my forehead, scalp, neck and shoulders.
If I feel my eyebrows furrow, I try to limit that and return my focus to the base of the skull or nape of the neck.
Following all this, if it's possible to do so, I try to be a little more understanding with myself. If there's no obvious reason for the crying, it may be that there's something of a block there, and that thorough exploration of the source might be needed.
For the real work, serious introspection and honest assessment is required. This process can be painful, but I can't stress enough that if you've actually gotten this far, it feels like the "right" kind of pain, and can lead to much better times.
Hey, I think this is a process much like any other. Crying is good to release that stress but if we've built up so much that it's haunting us day after day, it's an obvious sign -- like a warning light -- that we need to pop the hood and look at what makes us work. At the end of the day, prevention is worth a pound of cure. Stay in touch with yourself, stay true to yourself and when you mess up, forgive yourself and you'll be much better off than...
...uh, all of us, I guess.
Stay safe, guys.