From the outside looking in, it can be difficult to spot the differences between stress and anxiety. Both can lead to sleepless nights, exhaustion, excessive worry, lack of focus, and irritability. Even physical symptoms ā like rapid heart rate, muscle tension, and headaches ā can impact both people experiencing stress and those diagnosed with an anxiety disorder. With symptoms that can appear interchangeable, it can be difficult to know when to work on deep breathing and when to seek professional help.