I personally don't love the term "tough" love, as it implies a severity or spirit of mean-ness that has nothing to do with the intention. It's simply allowing someone the dignity of their personal life choices, but retaining your own dignity by allowing yourself the freedom to step away from the consequences of those choices. It's what we do when we allow our children to grow up and the only way that they can steer their own lives successfully is if we loosen our grip on the reigns.
What's tough is watching someone with choices, use those to bring themselves grief or hardship.