Dear (last year's) Katie,
You need to chill out. Stop worrying about the future. I know your tenant's haven't paid rent in 2 months, and school is getting stressful, but you need to take a second to relax. The next few months are going to be rough, but the evil-tenant's will eventually be evicted.
Do yoga, enjoy your friends, take time for yourself. Explore your passions, start dreaming! You are going to find a job this year that you will fall in love with. For the first time in your life you will wake up in the morning excited about the work you get to do that day.
Spend quality time with your husband. He loves you, and this med-school thing on a Caribbean Island is just as rough on him as it is on you. Take a walk to the beach, go out to dinner every once in a while.
You have one life to live, don't waste it on the past or future; enjoy your life right now!
With Love and Kindness,