Sharing credit shows self-confidence

Being humble about your work and sharing credit with others demonstrates the kind of self-confidence that people like being around. People appreciate when their contributions are publicly acknowledged. As a result, they're more likely to want to work hard to help you and your team succeed in the future.

Self-promoters have a bad habit of glossing over others' contributions. The worst offenders think that people are unaware of their antics. But, people whose opinions matter most know that anything meaningful requires a team effort. In the short-term self-promoters may be rewarded for their "contributions," but this'll quickly catch up with them.

On the other hand, when you're consistently on high-performing teams and share credit with those around you, people take notice. Trust that over time people are smart enough to figure out roughly how much everyone is contributing to projects.