Proactive behavior is more than just taking initiative. It involves a notion of response-ability. The ability to look for opportunities to formulate a response.
Reactive is putting out a fire - Pro-Active is fire prevention.
Reactive is bringing a glass of water to a guest who requests it- Pro-Active is placing an extra box of tissue on the bed table of a guest who appears to have a cold.
Reactive is taking care of flight reconfirmations at the Concierge counter - Pro-Active is the front desk clerk who asks the check-in guests if he would like to reconfirm his ticket now.
The great thing about proactivity is that most of the time, it costs nothing.
Have a great weekend!