Julian describes seven "great pains." The first is a "severe bruising." The second and third great pains are the "weight" of the servant's body and the "weakness" that weight creates. Basically, the first three great pains of sin describe being injured and incapacitated. We're hurt and cannot help ourselves. We've fallen and cannot lift ourselves up.
There is more to sin than pain. There is weakness and incapacity. Powerlessness. Impotence. This is Paul's lament in Romans 7:
For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate...Wretched man that I am!
This is the recognition of the recovery community in the very first of the Twelve Steps:
We admitted we were powerless over alcohol — that our lives had become unmanageable.
This is the hard truth that stares back at you in the mirror as you struggle, for decades, with ingrained habits and patterns of thought and behavior that stubbornly persist and resist all your efforts of reform and repentance. Sin is our chronic tendency to disappoint ourselves and those we love, in small and large ways. Sin is the lament that we are far from the person we wish we were, despite all our effort and striving.