Q : 
I didn’t fast sometimes on Fridays. Is it considered to be a mortal sin for not fasting on Fridays?
【 Question from 】 Malaysia 馬來西亞

Fr. Francis : 

Please first read
http://askfrfrancis.org/qa/does-elderly-need-to-abstain-from-meat-on-ash-wednesday-and-good-friday

Except for the prescribed days of fasting (in most places only Ash Wednesday and Good Friday) the Church today no longer sees failure to fast as a matter of sin, since punishment alone cannot invite hearts to voluntarily go beyond the mere requirements. The Church today sees fasting as a matter of voluntary religious discipline. So while failure to practise fasting on Friday is not a sin, it is necessary for us to perform some regular penitential acts including fasting for us to be able to grow in love and holiness. Failure to desire and embrace such practices therefore does harm to our soul.