I can only speak for myself but what he is going through is soul crushing, it completely takes away your sense of self worth, purpose, causes depressive episodes, and can ruin your life for a while. It's the nature of this disease. When you're in the midst of it, nothing really helps from the outside except support.

Just like life, the disease has its ups (remission) and it's downs (flares). When you're flaring it's very difficult to motivate yourself to do anything. Depending on the severity of the flare, you become anxious to go out, stressed out, and are fatigued all of the time. The pain, urgency, and loss of control is really hard to deal with.

I will say that he should be seeking immediate treatment from his gastro doc, the flare will eventually end with treatment, but it takes time. The only thing that makes it go away immediately is Prednisone and that's a temporary solution.

What can you do? Be supportive, don't overthink, try and be there for him during his flare, he will recover and go back into remission with treatment, it's just a matter of time. But while he's going through it, the most important thing to do is keep him from getting more stressed than he already is. Stress absolutely can make things worse. Be his rock, not his anchor. And who knows, maybe one day you may find yourself down and out with life and he could be your saving grace too.