The thing that helps me relax, and in turn helps them relax, is to at least spend a couple minutes doing something relaxing together.
For example: I have a friend who's an equine massage therapist. She came out a month ago and gave Red a little massage treat! (First time I have ever had her out.) She showed me some really useful "yoga" moves I can do with Red and specific areas he had knots that I can work on. So before every single ride, I take 5+ minutes to work on all his stretches and massage his trouble areas (he's got awful knots right in his poll, even I can feel them!). It's become routine for us now and he instantly goes into this eyes-half-closed and lips-wiggling posture when we go through it. Relaxing and calming for me and for him! Makes you forget about all you stressors and just think about the horse.
You could do this with spending some time grooming, if you don't know what stretches to do.
Not only is it good to come and here and vent with us (never a good idea to hold these feelings in!) but it might not be a bad idea to seek professional help occassionally. I did so myself while going through graduate school and spending 4 years apart from my husband. And it really, really helped. I feel no shame in seeking help, and no one ever should! Remember that that is always an option too.