If you think that a task is burdensome then you’re unlikely to want to do it. Rather you’ll avoid it as far as possible. However if you are given a task that is a joy and the strength to do it, then you’ll do it and rejoice. This is the difference between being a slave and being a son. If you are a slave you will crave freedom so you can avoid the task and hide from the job. Freedom for a slave is to not do what you have to do. For a son though, freedom is being able to do the task you’ve been given and rejoice in it. This is the freedom that God gives when he adopts you. Not that you are free from duties, but that you are free in your duty to obey and rejoice. John Owen puts it like this.
Slaves take freedom from duty, children have liberty in duty… The liberty of slaves or servants comes from mistaken, deceiving conclusions; the liberty of sons comes from the power of the indwelling Spirit of grace.
Communion With God – John Owen