I find that all too often, people in testing just glide through without trying to further themselves and improve themselves.
In the article above it highlights 6 ways that a sports professional can maximise their potential through the right mental attitude, I will take these and adapt them so that they can apply to a tester:
Focus on success
Focus on releasing successful software, (if that is the goal of the project), in fact we can make that broader by saying that we should focus on a successful project, and to be a part of that success and try and do everything you can to achieve said success. Try not to get drawn into focusing on negatives, which leads us nicely to...
Create a positive self-image
I've mentioned in the past about increasing your profile within QA, but this is slightly different in that it's about creating a positive self image across the company, and perhaps more importantly across your team. If you're positive yourself, then you'll find people will be positive towards you and your team, and positivity breeds success, so it does kind of relate to the first point above.
Define and work towards goals
These goals can be personal goals, or team goals. For personal goals they can be anything from driving some method of testing forward within your company (for instance Exploratory Testing) or for team goals, they can be to drive TDD as a team within the company and try and help other teams adopt the process.
Take personal responsibility
You need to be responsible for your actions within your team, if you make a mistake then hold your hands up, people are much more likely to forgive and forget if you are honest with them from the start.
I love a David Brent quote which is as follows "nothing ever changes by staying the same" and that is blatantly obvious, but it's surprising how many people expect changes to happen or improvements to happen when they haven't actually changed anything about themselves. If you see a weakness in your skills then drive to improve it, if you're not good at communicating then look at ways you can improve it, or technical skills can be improved easily by taking courses online in your spare time.
Learn from others
Perhaps one of the most important things here, and that is we need to learn from others within our team, within our company and within the wider QA community. On the flip side, we ourselves need to be open about what we know, and share the knowledge, otherwise nobody learns anything from anybody and that's just not a very healthy environment to be in.
Can you think of anymore mental attitudes you can adopt to help become a better tester? or a better professional as looking at the list, I believe it can be adapted to any profession, (as I have done..) and not just sports or testing!