The Law of Karma

[An] important thing Hindus believe in is called the law of karma. This law says that everything we do will produce certain results. For example, if we work hard at school, we get good results. If we do not work hard, we get poor results. Everything we do adds up and produces good or bad, or mixed results. This is why we have to be very careful about everything we do. Sometimes the results of what we do catch up immediately, sometimes they take a long time to catch up with us. This is why people sometimes use the phrase my Karma is catching up with me. If we act very badly, it is not God who punishes us, but the law of karma catching up with us and making us pay a price for the bad things we may have done.

Imagine that you have a test in school tomorrow. You have a lot of studying to do. But then your favourite TV programme is just about to start. You really want to see that programme, but if you don't do your revision, you will do badly in the test. You choose to do the revision. The next day, you do well in your test: You feel pleased with yourself. You had a choice between watching TV or doing revision. You chose well, and good results followed. You were in charge of what you did. The law of karma then rewarded you.

Reference: Primary Hinduism by Seeta Lakhani (Ch.4, 'What Hindus Believe', p.47)