The top five things to do are;
Sleep - We all need at least 6 hours of sleep per day. Sleep allows the brain to 'defrag' itself after the days events.
Exercise - Just a 30-minute walk per day is all that is needed to get that oxygenated blood flowing around your brain and to produce endorphines.
Socialisation - It is important to get out of the house and meet with others, talk about your problems, share a joke, and stimulate your brain. We tend to shut ourselves off when under stress.
Positive thoughts - Stop your brain from having negative thoughts by replacing them with positive ones. Thinking happy thoughts retrains the brain to reject unhappy ones.
Look Forward - Always look for forward to something in the future that you are excited about. It may be getting to the gym at the end of the day, a great trip planned for the weekend, or an up-coming holiday.