Diana Nyad attempts fourth Cuba-Florida swim

(CBS News) 62-year-old long-distance swimmer Diana Nyad is looking to hit two milestones this week, but only one of them is a sure thing. Nyad will turn 63 on Wednesday and hopes to complete her fourth attempt to swim from Cuba to Florida on Tuesday.

During her previous attempts, Nyad faced a myriad of challenges. Her third attempt ended with paralyzing jellyfish stings and an asthma attack.

This time around, the swimmer is wearing a special suit to protect against jellyfish stings, but Saturday night she still faced a barrage of jellyfish stings, including on her lips and forehead.

Now, two days into the 103-mile marathon swim, the swimmer told KPHO's Tammy Leitner that she fights the monotony of the swim through shark-infested waters by singing to herself.

The endurance athlete hopes to hit the Florida Keys by Tuesday.

Dr. Patricia Donnelly, a mental fitness coach, joined "CBS This Morning," to discuss the challenges and reasons behind Nyad's drive to complete this lifelong goal.

(To watch Donnelly's full "CTM" interview, click on the video in the player above.)

"What's she's trying to do is a first. She's trying to conquer one of her challenges in life," Donnelly said on "CTM," "We all have a Mount Everest that we want to climb. And, this is hers."

The coach and psychotherapist also added that while Nyad is in peak physical condition, much of her struggle is beyond sheer athleticism. "An enormous amount is mental," Donnelly said.

To watch the full report on Nyad's swim, click on the video in the player above.