Well, no. You need to have the capability to back up good intent. In any endeavor, you need to actually deliver and for that good intentions are not usually enough.
Let me give you an example. At work, I know a few people who are very sincere, very enthusiastic and eager to do well. But they are unable to back it up with results. Tch, tch. Doesn't help.
I have utmost appreciation for their attitude but I'm afraid, they are not effective at delivering things as needed. Successful people are, to borrow from Joel Spolsky, people who are smart and get things done.
Good intentions are important. But that's not all.
I feel a little sorry for these people. I want them to do well. I really want them to succeed. I like them for their attitude. But I cannot trust them with important work and that's sad.
On the other hand, you have the capable guys. With loads of attitude, albeit the wrong kind. They have the ability to do whatever is required. And do it fast. But you need to pamper them, praise them, mollycoddle them. Only then can you get the work done. These guys couldn't care less if the work doesn't get done if they don't contribute.
Great attitude with great capability - a killer combination. But difficult to find.