How can the Almighty’s saying, "So that you do not grieve over what has escaped you, nor rejoice over what He has given you," be applied, especially concerning rejoicing over what comes to you? Does this mean not rejoicing over any achievement, or not exaggerating in joy and taking only a little of it? And how can a person live this moderation?

Your joy in your accomplishments is not blameworthy unless it leads you to ingratitude and arrogance, and causes you to become conceited and proud, and makes you forget your share in the Hereafter.

If your joy includes attributing the blessing to Allah, thanking Him for it, and spending it in ways that please Him, then this is a joy that is permissible. This is achieved by knowing that everything is predetermined by Allah, and that every blessing is purely from His grace.

The intent is to negate sorrow that leads one to lose patience and submission, and to negate excessive joy that distracts one from gratitude. As for moderate sorrow and joy accompanied by gratitude, there is no harm in them.