From metawiki
René Descartes: "I think therefore I am"

Subjective refers to the experience of a thing in the mind of a conscious being, and all of the emotions, memories, thoughts, and other reactions that it triggers.

It also deals with matters of opinion that have no "right" answer independent of the individual, such as "what is the best movie?"

You can exert significant influence over your subjective emotional experience using various techniques like mindfulness. It is better to greet experiences in life with a universal sense of positivity in order to maximize the happiness that your subjective experience provides you.

See Subjectivity and Objectivity on Wikipedia.

Subjectivity vs. Objectivity

Joelaul x Jake Howsam Lowe - Subjectively Objective