The challenge here is to try not to get into a struggle with being awake when you’d prefer to be asleep, because the more you resist it, the more it will agitate the mind and make getting back to sleep even harder. If you’re lying awake, see if you can let the out-breath become slightly longer than the in-breath, which can help to calm the nervous system. Sometimes simply placing one hand on the heart and one on the belly can be a physical reminder of self-compassion, too. Loving Kindness meditation can be really helpful, Sharon Salzberg teaches this practice in our course 10% Nicer. You may also benefit from trying some short guided self-compassion meditations - for example, Kristin Neff has a few here: http://self-compassion.org/category/exercises/
Lying in a state of meditation is more restful than just lying awake ruminating, so try to relax into knowing that you’re still getting some kind of rest, even if it’s not actual deep sleep.