Waid lightened up DD, since the character is normally beaten down so much.
Although he did a great job of making the "lighter" Matt a believable continuation of, and reaction to, all the darker stuff in his past. The darkness was still there, underlying it all, but he was actively resisting it by choosing to adopt a lighter outlook -- to the extent that Foggy even feared he was in denial and perhaps even mentally incompetent.
It's worth noting, though, that Waid was also bringing DD back to his original Stan Lee characterization. DD and Spider-Man were almost identical characters in the early years -- acrobatic, fast-talking wisecrackers in red tights, swinging from rooftops and aided by enhanced senses that alerted them to danger and let them perceive the unseen. (Indeed, Lee wrote Spidey's spider-senses as enhanced sensory awareness of objects and movements around him, rather than the psychic danger sense it was later presumed to be, and even showed Spidey using it to find his way in darkened rooms or locate hidden passages, just as DD's radar sense could.) Miller's dark, revisionist take on Daredevil probably made him a truly distinctive character from Spidey for the first time (as far as I know, since I'm not that expert on DD's history), but I feel that Lee's (and Waid's) carefree characterization made more sense for someone known as "Daredevil, the Man Without Fear."
I felt there was a degree of Waid's DD in Matt's characterization this season. He seemed to have become more cocky and self-assured since bringing down Fisk and adopting the costume, more convinced that he had the answers and was in control of his life -- which ended up becoming his biggest problem, because his arrogance led him to believe he didn't need anyone's help, so he isolated himself from his friends and allies. And Elektra appealed to his thrillseeking side and drew him in deeper.
