It wouldn't be too much of an oversimplification to say that, for most people, happiness is determined by three sets of factors:
- Objective external circumstances and events
- The person's subjective perception of those external circumstances and events
- The person's expectations and standards, to which those external circumstances and events are being compared
This immediately suggests three potential routes to happiness:
- Act in a way that causes good things to happen to you, for example, by working hard to give yourself better future options.
- Think about the things that happen to you in a way that focuses on positivity, for example by finding silver linings and appreciating what you have rather than lamenting what you don't have.
- Have realistic expectations about the future. Or, if you are able to delude yourself, have slightly pessimistic expectations about the future, so that you're pleasantly surprised by how things turn out.
The optimal approach is probably a combination of the three.