First, even if you happen to know that another coworker is making more than you, Valentin says don't compare your pay in your negotiations. "This can create awkwardness and can distract from your key arguments. It’s better to focus on your own value and achievements."
And don't mention your financial situation during a negotiation either. "Things like wanting to get a dog or needing to upgrade your car, though, could be very honest reasons for wanting a raise, but aren’t a compelling reason for deserving higher compensation," Valentin explains. As someone who made this mistake at one of my first jobs, let me tell you, they did not care, and it did not work.
Finally, don't rush the process. "It may take a little time for any raise to be signed off on internally, so don’t expect immediate action. If necessary, ask your employer for a follow-up conversation to discuss the outcome. In the meantime, remember to thank them for their time."