Someone doesn't challenge himself as often, as consistently as Riku does without a keen awareness of his own limits and shortcomings. He knows the temptation to put his own healing aside for the sake of another - for a friend - would have easily outpaced the need for that time to recover. He knows he wasn't ready, didn't have what it took, he would have spent up what little he needed to spend on himself at best, he would have self-destructed at worst. He very nearly did, at the very beginning, when Bruce tied him up for his own good.

Riku, who has never been very good at putting into words the things kept closest to his heart, is used to his motives and priorities being misunderstood - even his best, dearest friends found his actions mysterious and questionable sometimes, when the answer was typically as simple as this: everything he did was for them.

He's been trying to get better.
Some of it is to fulfill his promise to Sora. To survive. To be the lighthouse that brings him back.
Some of it is an obligation to not burden his friends with the consequences of his own habitual neglect.
A little is out of recognizing that strength can come from vulnerability, too.

Except Riku bucks against the requirement to lay bare his heart, to show how near a miss it had been, how sick the place his thoughts had been in when he was convinced that some cruel twist of fate and his own failings to protect had torn from him everything that ever mattered.

He just can't do it. He won't. M.K. says I see and Riku does. He knows he's burned a bridge with this. It feels terrible. Riku is also poor when it comes to reconciling with loss, unwilling to explain and unable to clarify his position, he instead gets angry, defensive.

His temper has ever been a stumbling block.

"Why do I have to spell it out for you? What makes you more special than anyone else?!"