Helping others is good for you. Numerous studies have shown that helping people leaves you feeling happier. It causes your body to release dopamine which makes you feel more calm and happy whilst also reducing pain. So there is actually a scientific reason for feeing better. When you see the gratitude on the face of person you are helping you empathise with them and this too makes you feel better. Volunteering can also make your own problems seem much less significant when compared to others or just take your mind off them for a bit.
And finally, a study done in an American university medical centre showed that patients recovering from heart problems who volunteered to visit current heart patients recovered 60% faster than those who did not volunteer!!