On the New Taoist Community forum a poster was asking for advice on dealing with the feelings arising from a relationship breakdown. FWIW, with some modification for tense & context, here's my response...
Tears and emotions are the natural response to loss. They're not good or bad - they just are what they are. When going through a grieving process, the emotions need to be released. They should be let out in the knowledge that they're part of a natural process and will lose their intensity over time.
Negative thoughts are also natural at such a time, but they don't really achieve anything. IMHO their source is the conflict between the image of the future that has been held for a long time (e.g. married & family life), and the image of the future that is developing now. Both of these images are illusions. We can guess, but we don't really have any idea of how our lives will be 1 day from now, let alone over a course of years; and our memories of past events are merely distorted reflections. All we have is right now. The past has happened and nothing can be done to change it. The future is a path to be walked and experienced, an adventure into the unknown that always starts from where we are.
When you find yourself getting wrapped in negative thoughts, try concentrating on being solely in the present moment. Notice how the light reflects on a glass of water. Concentrate on the taste and smell of the food you're eating. Observe the shape of the clouds. When you get consumed by thoughts of what you should have done, what you could have done, what you're going to do, and what you might do - take a deep breath, let it all go, remember they're all just tricks our brain plays on us which are of no real use. Try concentrating on the here and now, on the small and mundane, the breath going in and out, the feel of the things touched. When the negativity starts returning, understand it's natural but of no use, let it go and then gently return to concentrating on the present moment again. The drifting into negativity is natural but can be poisonous, for example leading to anxiety or self-loathing, the concentration on the present is the antidote.