And how do you deal with it ?

Sometimes you just have to walk on...

Sometimes you can try to 'fix' the problem, and sometimes the problem is not something that has to be fixed.

If you are out of your depth, refer your client on to someone else. Death and dying is not everyone's gift.

At our church in Australia we buried one close member of our congregation every year for 6 years in a row. Young man with melanoma, wife and two small children, another man in his 50's who had recently retired developed Leukaemia, an elderly lady of 90+ years who suffered for many years, another lady who thought her life would finally improve now she had managed to separate from her abusive alcoholic husband and then was diagnosed with cancer and given 6 months to live, we seek justice and we do not find it...not in this life...

The question is one pondered for thousands of years. Religious texts are often the most accessible source of ideas of how the previous generations dealt with these issues.

There is no answer. One question leads to another, but I don't think you can have an answer to human suffering...