There are a lot of personal attributes and social behaviors that unlock opportunities. In the US a positive attitude, gratitude, and genuine interest are among them. In general just being pleasant to be around and personable will get you far in the engineering world because those qualities are often times lacking. When people managers are making decisions about resourcing I think that they are not honest with themselves about how much them 'liking' a person goes into their decision making process. Same for hiring.
If you are a terse and dour person, it isn't that you will experience more rejection per-se, it is just that opportunities will not even be presented to you because the person with the opportunity doesn't want to spend time in your presence.