Mental health: I believe that mental health is most important correlation to physical health. Stress, grief, etc can cause physical problems, in my opinion. (Article from The Truth about Cancer on this issue & a good post from Rachel Sheer on this how lifestyle/mental health could improve health.) Please do everything you can to stay in the best/calm mental state as you can, and try to not contribute to mental stress / suffering of others.

Physical exercise: Don't worry about metrics or body type/weight. Just try to do light weight training to have good muscle tone.

Diet: Listen to your body. Try not to eat or overeat, eat until you are comfortably full. Don't think about all or nothing, but try to eat more healthier whole foods, and avoid processed sugar and artificial food dyes. Try to stay hydrated, get enough B vitamins, especially B-12 and electrolytes, and see which foods make you feel better long term. Organic apples or applesauce are good for digestive health.