As he logged on to his online 401(k) retirement account, Jordan Tirone, a 25-year-old insurance underwriter, explained the mental accounting behind his 5 percent contribution. He pays $300 a month to live with his mother so he can pay off student loans. Nevertheless, a regular paycheck from his Hartford, Conn., employer is finally giving him some financial stability. “I’m feeling like I’m gaining some traction,” he said. Spontaneously, he clicks his mouse and increases his contribution to 6 percent of his salary. Although it can be difficult to focus on a retirement that is still 40 years away, many young adults like Tirone try very hard to save. But are they doing enough? A lot of evidence suggests they’re not,…