How does one stay fulfilled performing obligations and yet remain detached?

Detachment comes when your attention shifts to something higher. So, let’s say your obligation is to do your job. You are an employee in an organisation, your obligation is to do your job, your obligation is to look after family and so on and so forth. But your interest is in self-development in the spiritual field. So, that is where you get attached and to that extent, you become detached from the lower.