What two or three personality characteristics are needed for me to be a successful as a computer engineer ?
Diligence, determination, intrinsic motivation are three that come to mind immediately. Of course, even though this career may not throw you into the social realm (face time, I mean, not social networking through computer-generated and long distance socialization which gives some anonymity), you still need some people skills as well.
This may sound obvious, but all the computer engineers I have known love their job because they love computers and spend all their time, in work and out of work, on computers and "talking" to them. Therefore, in addition to self-motivation and being detail orientated, I think it is vital that you have a real affinity for computing work. After all, if you are successful you are going to spend the majority of your working life interacting with a computer screen, so you need to like that now!
I agree that you would have to be self-motivated. But I also think that it is very important to be a person who is very attentive to detail. A computer engineer has to be meticulous and very careful because of the complexity and detail involved in the job. A computer engineer cannot be someone who likes to just "wing it."