The key features of projects that contribute to well-being are meaningfulness and manageability. Meaningful projects align with values, are enjoyable, and express who you are. However, manageability is also crucial for well-being. Projects must be manageable in terms of successful completion, control, coherence, and time. Meaningful projects that are also manageable enhance well-being, while those that are not manageable do not significantly impact subjective well-being. The most important aspect of personal projects is the sense of efficacy, the belief in the likelihood of successful completion. Projects that are both meaningful and manageable lead to greater happiness compared to those lacking manageability.