Ajahn Pavaro reflects on the expression in the Metta Sutta..." unburdened with duties". He asks how do we regard our duties? How could we simplify and reframe them ?
He references Ajahn Viradhammo's use of the foreground and the background and how the practice of mindfulness helps us to know the background. If we attach to the sensation that arises - we are then in the foreground. By attending to what is happening a wholesome, causal relationship begins to develop (bhavana) awareness of the nuanced movement between the foreground and the background.
Ajahn directs us to the body as a frame of reference and recommends Frames of Mindfulness by Ajaan Lee Dhammadharo, translated by Thanissaro Bhikkhu. https://www.accesstoinsight.org/lib/thai/lee/frames.html