Ok, not suprisingly, the easiest habit for me is Play. I make a conscious effort to enjoy life and play is a big part of that, in both my personal and professional life. As a manager, I try to make my employee's work-life enjoyable as well. We all spend so much time together that it's ridiculous to be miserable or to dislike coming to work.
The hardest habit for me is viewing problems as challenges. It's semantics really, but I get what they're saying. I tend to get immediately overwhelmed when a problem presents itself. I'm not really into challenges, I'm more laid back and easygoing. What I need to do then, at work at least, is to think about how problems may affect my co-workers and approach the challenge that way. I should see the issue as a challenge to be resolved for the team.