Ps 51:12 Restore to me the joy of Your salvation, And uphold me by Your generous Spirit.
Let us take another example; an indicator of a healthy marriage lies in the joy of having been married. Even though there are storms in life during that marriage, internally the joy of husband and wife being together in any situation brings internal joy and happiness in the midst of problems. At any point of time if one of them lose joy or the joyfulness of being together is reduced then it is the sign of problem within that marriage. If it is not rectified then slowly it will go to a divorce or just a namesake relationship. Likewise when our joyfulness in His salvation is not the same or more from day one, then it is an indicator of a problem in our salvation or in our relationship with Jesus Christ.