Well ,we ave all been there..trying hard to keep cool around competitive people.Weather its your spouse,boss,friend,colleague.. People can be competitive and their are ways one can deal with them.I may not have all the answers but I will pick out three group of people you can deal with when they are competitive.
If your manager is competitive,their is every possibility they see you on their turf.If you notice this,step outside yourself to catch a glimpse into your manager "s perception.The more you can mirror back your boss goals and needs,the better.They will know you are on the same page.
If your colleague is competitive,their are two things you can do.You can have a private chat with him and make him understand that you are allies not adversaries and you have to work together to be able to meet the goal of the organization.If on the other hand your colleague is taking credit and stealing your ideas,then out need to stand up for yourself.
If your romantic partner in the same field is competitive,drawing clear boundaries will preserve your relationship.This lines should limit comparisons and encourage collaboration and support.