Providing feedback sometimes presents a challenge because it seems to be ignored often, or used as a basis for arguing about a grade. I always try to start with some positive feedback (what they have done well, or at least the demonstration of an effort), which I think aligns with the “self” level. After that, my feedback tends to focus on what the student failed to do or areas that need improvement, which aligns with the “task” level.
Where I see a gap, is that I sometimes lose focus of the goals and just concentrate on how well the task was accomplished, rather than how well they worked toward the goal that was set. In recent years, I have developed marking rubrics, that I share with the students at the same time as I discuss the assignment. In this way, the goal is clearly laid out for the student and they can see the different degrees of attainment for that goal. When I mark with a rubric, I am then more precisely focused on the goals rather than the general quality of the work or other considerations.
I think the optimal way to provide feedback is as part of a conversation with a student, where they can also contribute to the feedback process by stating what they believe they have done well and what gave them more trouble, and we can come to an understanding about appropriate steps to take moving forward (“feed forward”).