It is often said you are a reflection of a few people you spend the most time around, so are you making good decisions about who you spend time with? As a triathlete, I know if I spend more time with fellow athletes, I will work out more. The other week I did a 30+ mile bike ride with some teammates. It was freezing weather (17 Fahrenheit/-8 Celsius) and we rode for over 2 hours (at which point my water bottles were frozen solid). I would never have done a crazy ride like this on my own, it was only because of the people I was with that pushed me to go so far.
The same thing can be said of our work-mates. If you're always spending time with the person complaining about how they don't like their job, you will start getting a negative attitude. If you spend a lot of time around a workaholic, you'll probably find yourself working more hours.
A lot of times we don't have much control about who we work with, but there is something you can do. Find someone that has those skills you want to improve on; maybe being better at public speaking or being more proactive. Now ask this person if they would be a mentor for you. If you spend even a couple half hour sessions a week, they will start influencing your behavior. It could be as simple as having coffee one day and lunch another day (you can usually decide who to spend lunch with).