Severus returned the smile, rueful for so many reasons.
"And I greatly regret that my duties - then and now - have kept me busy elsewhere." He regarded Draco sombrely. "Still, I count my attempts to protect your younger self as effort very well spent - even though I wasn't as successful as I'd hoped.
You've turned out admirably," Severus mused aloud, "frankly I never thought I'd live to see the day." A blackly humorous laugh. "Of course, barring this time-twisting little miracle, I didn't."