Looking into some assertiveness training may help you to handle your tenants and bosses better without being pushed around or breaking down. You don't necessarily want to be aggressive (a lot of people confuse these two behaviors), but you want to be able to handle yourself in a way that gets the job done without bending over backward for people.
I agree with getting a personal organizer. If you phone has an agenda app you can have it alert you a day or a week before something is due, or have an alarm set. Have a schedule laid out for your day with some "extra" time for when unexpected things pop up.
I also think you should look into some personal help for yourself to better manage your emotions. Depression, whether it is due to your job or other things, can greatly impact your performance in many areas of your life. Seeking counseling, medication, herbal remedies, and having a variety of coping resources (e.g., meditation, stress ball, whatever works for you) will be very important.
A lot of times these kinds of issues don't just have one easy fix. You'll have to play around with some different approaches to dealing with stress and assignments. Don't become discouraged if one thing doesn't work for you. Just give it some time and then move on to something else if it doesn't help.
"Life's journey is like driving at night in the fog.
You can only see as far as your headlights,
but you can make the whole trip that way."
Chronic Lyme, Depression, Anxiety, 12+ Years