The keynote speaker at my sister's graduation, Kent Alterman, president and CEO of Comedy Central, gave some memorable advice that I still haven't forgotten. (PS, I don't even remember who spoke at mine.)
"Don’t look backward because that causes depression (plus the past is rarely as good or bad as we remember it to be). Don’t look forward because that causes anxiety (plus the future is rarely as scary as we imagine it will be). Be present in the moment because that is the only time that is truly authentic."