The women at the well is a well known passage but I think in our becoming familiar with these words we have forgotten the power of the Word - God's revelation!
First, let us remember the passage. A women was at the well in the middle of the day, lots of historical/ cultural experts tell us this would be unusual. Women usually fetched water at the beginning or end of the day and would usually do so in groups. Her coming alone could be a sign of her being an outcast perhaps because of her sins.
Second, let us keep in mind that she didn't go to the well that day looking to be changed, looking for something different. She wasn't expecting anything more then to fetch water as usual.
Third, when Jesus offers her forgiveness - she is activity sinning. She hadn't asked to be forgiven or promised to stop sinning.
Fourth, we have no idea what happened to her. We know from later / other passages that some people who had been sinners but believed and trusted in Jesus followed him around - but we don't know if this women did. We don't know if she went back to the man she was with or not. In fact if we think about the social / cultural stuff we would assume she did go right back to her former life - what would a women like her do if she gave up her life, would she become a beggar?
So what is the lesson for us? The power punch in this story is that God forgives us EVEN when we are activity sinning. That the power in the forgiveness isn't God forgiving us but is in OUR acceptance and in US allowing the forgiveness to transform our lives. It is pretty easy to have a feel good moment with God and then go on doing what we humans do - sin. It is more powerful to change our lives and allow forgiveness to be transforming.
Look at those who followed Christ and gave up their ways, they had a much more meaningful transformation.
The power in accepting Jesus as our true living water is to be willing to let the forgiveness be the final one - not keep sinning or stay in the cycle of non-accepting. Let us accept forgiveness, we don't have to already be stopping - we can choose today to live a more transformed life.