A few years ago I came across this quote, attributed to the famous Chinese philosopher Lao Tzu:
If you are depressed, you are living in the past.
If you are anxious, you are living in the future.
If you are at peace, you are living in the present.
– Lao Tzu
It resonated extremely strongly with me, as I'm the type of person who's often living in the past or the future. You can only find peace in the present and we must never forget this. Living in the present, however, is a lot harder than it sounds.