Fabricio this is such a simple yet important point that applies to ANY type of design work. Even more so to complex work like web UI design. As you pointed out, every piece is always part of a larger system, and you’re doing yourself a disservice if you try to polish up a little part before making sure the whole system is evolving in the right direction. The only way to do that is to work in layers of fidelity.
Involving the client (and sometimes users) in this process also helps everyone feel a greater sense of ownership and commitment to the project.
Thanks for sharing such a crucial piece of the ideal design process.