Lines can be delicate, deliberate, hard and sensitive, depends on how they are put together. As an archtect, I live with lines for longer than half my life. I create them, eliminate them, love/hate them and for most part, live and survive by them.
Now that I am back to create them purely for pleasure on sketching, drawing them, I confess that it's only NOW that I realise I am just starting to LEARN about lines, and working very hard to try to KNOW and UNDERSTAND what line is, for now it becomes part of my thought and expression!