The imabima has been blogging her #BlogElul and #ElulGram for quite a few years now. She takes various aspects Teshuva and assigns them to a day of the month of Elul.
Teshuva is translated as "Repentance," but what it really means is more complex. A few years ago, I attended a course by Rabbi Reuven Grodner in Pardess which taught us about the concept, the act of repenting and what it is for Jews.
Teshuva is multi-dimensional. It's not just a simple act of being "sorry." We must reach the level that if/when we find ourselves in the same sort of position, we now act properly and don't sin. Proper Teshuva demands a lot of growth and change in ourselves.
Teshuva is a never-ending process. None of us will ever be perfect enough to say that we no longer have to "do Teshuva." As high a level we achieve in our spiritual quests, there's always a new challenge.
We must also remember that Teshuva is not reserved only for the Jewish Month of Elul, it's a process that should fill every single day of the year, Gd willing.