The useful side
Deep engagement can be productive, creative and enjoyable. It may make it possible to work through a complex problem or learn an enormous amount about something interesting.
The awkward side
The same absorption can make it difficult to notice hunger, messages, appointments, people speaking or the fact that it is now 2am. The issue is not that focus is inherently bad; it is whether control over entering and leaving it is reliable.
Build an exit ramp
Use external stopping cues, visible clocks and planned checkpoints before starting something absorbing. If another person needs your attention, agreeing how they should interrupt can work better than assuming their first attempt will register.