I know the whole mamasan thing but I think this song is actually happy despite the angry tone. I think it's about a person that was held back by their own thoughts. (Once upon a time I could control myself.) Then they realized that there wasn't anything holding them back so they accomplished what they needed to after breaking from their own limits. So I think this song is of celebration after becoming a new more brave person.
I know the whole mamasan thing but I think this song is actually happy despite the angry tone. I think it's about a person that was held back by their own thoughts. (Once upon a time I could control myself.) Then they realized that there wasn't anything holding them back so they accomplished what they needed to after breaking from their own limits. So I think this song is of celebration after becoming a new more brave person.