Get to know God and yourself first. Pray A LOT about this and reflect on this before acting alone. Acting alone on this is NOT a sin, but it could be VERY unwise depending on various factors.
You might think along the lines of some kind of fasting or abstinence.
The eastern churches fast about 6 months out of the year.
Our Roman church fasts 40 days of lent.
More fasting would be good if you are healthy.
Abstinence is also good, especially from our modern conveniences and entertainment.
Then replacing that time with prayer for sinners and the world, or personal reflective prayer.
Another form of mortification is always to do what you know God wants you to do.
That is, pray more to know his will, and then make your will bend to his.
This is the toughest kind of mortification, to do Gods will every moment in the day.
So often what happens is that we decide first what to do, determine if it ok before doing our will without considering God’s will first which may be different.
If you do decide to do something along these lines, you will notice a difference in your connection with Jesus. For He is never out done in generosity.
Just some thoughts.