Can justice be compatible with mercy?

Justice and mercy are not incompatible.

Human justice and divine justice have little in common besides the principle. Divine justice is based on absolute knowledge and takes into consideration all the circumstances. For instance, when you leave the earth, no court sits in judgment―no sentence is passed. 

The only judgment you must submit to is the inevitable result of the law, which brought you into being, and which declares that every act and thought of your earth life sets in motion waves or impulses either good and harmonious with their divine origin or bad and inharmonious.

Since you have a soul, which is a part of that great Creative Spirit, and which must ultimately come into perfect accord with that creative force, it follows that the waves of dissonance must be accorded.

If you create either in your earth or afterlife sufficient waves of good, they will neutralise the bad.

A true and worthy life on earth places you in a better position for further effort than a life, which has created discordant waves. It is the discovery of this law, which is your only judgment―

God’s justice sees each tiny effort and aspiration, and these influences are great. 

Since you must submit to the inevitable result of this law, and you will ultimately reach perfection, why make an effort on earth to do anything that will interfere with your fancy if you will be eternally happy sometime anyway? 

Why not be as happy as possible on earth in your own way?