expression
casual; lighthearted; without taking it too seriously
Describes an attitude or approach that is relaxed, not deeply committed, or lacking seriousness. Often used when someone does something on a whim or without much thought.
軽い気持ちで始めた趣味が、今では仕事になった。
A hobby I started casually has now become my job.
彼は軽い気持ちで言っただけだから、気にしないで。
He just said it lightly, so don't worry about it.
Compound of 軽い (light, not heavy) and 気持ち (feeling, mood). The phrase literally means 'light feeling' and is used idiomatically to describe a casual or non-serious attitude.