Ways to talk about regret, the act of regretting
Choose the way of translating this concept based on the meaning you're trying to get across. Some of these may also be appropriate translations of the word "melancholy."
trikar par ruyot: sadness for the past
echoy par ruyot: mourning for the past
vercopase par ruyot: wishes for the past, dreams for the past
echoylir ruyot: to mourn the past
vercopaanir par ruyot: to wish for the past
In some contexts, simply using echoy (mourning) might be appropriate.