Romans 12:15 (1–15) “Rejoice with those who rejoice, and weep with those who weep.”
The next gift Paul mentions the Holy Spirit giving us is the gift of mercy (12:8), and the advice for that gift is found in verse 12:15.
In technical terms I have defined mercy as God holding back what we deserve and grace as giving us what we don’t deserve, but in practical, day-to-day terms the word mercy involves both ideas. Yet, it is extremely hard to show mercy, of any kind, to some people.
This is why Paul urges us to show mercy with cheerfulness (meaning whether we like it or not). For the one with that gift it is much easier than for the rest of us. But, mercy is not just about what we deserve, it is about we need. All of us need not to be alone no matter if we are or are not the cause of our situation. As believers we need to be there, for each other, whether we feel like it or not.
But, it has been noted that those with the gift of mercy can begin to identify with the person they are comforting too closely and take up their cause. It is then that they forget their mandate, 12:15. Then they rejoice for few and weep for only that one.
Virtue involves allowing the Holy Spirit to remake us in the character of Christ.