As an investor managing my own money, saying no is the most important thing. As a person working in a team, that's not the way to go: It totally depends on who

As an investor managing my own money, saying no is the most important thing. As a person working in a team, that's not the way to go: It totally depends on who do you say no to (cross-team, teammate or manager). If it's your boss/manager, and the task is not that small, it's important to ask the priority compared to other goals, as it probably makes other goals unachiavable. Also the boss has better context on how important it is, so I would never just say no instead of asking for context. If it's from a cross-team and big thing, communicate with your boss and ask if it's important enough to change priorities. If what somebody asks makes sense, do it.