The most important characteristic
What dependability is
Dependability is the quality of being able to be counted on or relied upon. Be someone that a person can depend on is more that just saying that you will do something, it's actually doing it. When someone depends on you they are fully trusting and putting all their hope in you and it's your job to follow through and do whatever you said.
Why it's important
It is important to have the trait of dependability because it presents a good picture for your self. Not only that but if people know that you are a dependable person they will be more apt to help you or ask for your help.
Dependability; like Donald here, you can always count on him and believe what he says he's going to do.