Who do I need to forgive?

A week or so ago, during a quasi-devotional session, I had a Biblical reference etched right in front of my eyes. Of course, it flickered between a couple books, Matthew and Luke, and then I received a couple of numbers, 6 (for the chapter) and 15 (for the verse). Long story short, it turns out the Gospel of Matthew, chapter six, verse fifteen (and fourteen as well, since they go together), was what God wanted me to read.

If you forgive those who sin against you, your heavenly Father will forgive you. But if you refuse to forgive others, your Father will not forgive your sins.

--Matthew 6:14-15 (NLT) ["http://www.biblegateway.com/passage/?search=matthew%206:14-15&version=NLT"]

Then, as it often does, the thought faded away, thanks to amnesia. It was kinda like, ok, I need to forgive so God can forgive me... whatever..., without actually taking time to let it hit me. Well, that happened today. Sort of. Basically I was left with the question, "what or who do I need to forgive?" as well as the sister question "what sin(s) do I need to repent today?" I'm still figuring that out. If anyone who reads this receives words of wisdom from God -- i.e. a vision or something (and it has to be genuinely from God and not just something you want me to do or to hear) -- please tell me.