Yashar (upright) vs Tzadik (righteous)

Malbim (Mishlei 11:3): There is a distinction between yesharim (uprightness) and tzadikim (righteous). The yashar is one who naturally goes on the upright path – whether it is in religious thought or matters of understanding. That is because the majority of issues concerning yashar involve understanding (binah) or moral traits and deeds that are rooted in wisdom (chochma). Therefore when it comes to matters of wisdom (chochma) the yashar is distinguished from the tzadik in that the yashar naturally has the inclination in his heart to do good because of the uprightness which is implanted in him. In contrast the tzadik's conduct is based upon having learnt what righteous behavior is and constantly practicing it until the tzadik conquers his baser drives and trains himself to do the opposite of his nature. The yashar is simply expressing his nature. Furthermore the yashar is not concerned with the letter of the law but is concerned with the spirit of the law - until he conducts himself beyond that which the law actually requires…. Therefore in order to go in the good path it is needed that 1) his path is yashar and 2) that he is aided in going in that path. … Thus one who is not yashar, his path is not yashara and he needs help from Above to straighten his path. Even though the yashar conducts himself in the manner of uprightness because of his inner nature, nevertheless his physical needs sometimes cause him to deviate from that path. But if he has the additional aspect of temimus (purity) he will be totally consistent in his conduct of uprightness and not deviate from it because of physical needs….