You have to recognise that the pressure can be phenomenal. I still don't think this guy necessarily killed himself because of work stress. However, if he did, then it doesn't necessarily surprise me.
It can be the unrelenting nature of the work which can cause the problems. The stress of dealing with clients, your colleagues and your opponents. Its not the long hours per se, but rather what happens during those hours which is so stressful. Simply saying "Well, you knew what it was going to be like" isn't much compensation when you're returning home exhausted night after night.
The work stress can easily lead into other difficulties (relationship breakdowns, alcohol/drug dependancy, illness thru poor diet etc, gambling etc). Its incredibly easy for it to happen and for things to get on top of you. I had a period at work, for approx 4 months, when I worked late most nights (eg 9 or 10ish) and was often in the office for some time at the weekend. I wasn't doing all-nighters or spending 7 days a week in the office. But the cumulative effect was horrendous. I lost touch with friends. I'd hope that my cab got home before the off-licence shut so I could buy some booze. I had no time to exercise and my diet was appalling. You can easily feel that there's no escape from the work and all the other things that go with it. The important things to do, when confronted with work stress such as this, are:
(a) recognise there's a problem and that it doesn't represent a failing on your part. You're no less of a lawyer or person if you say "I can't deal with this"; and
(b) raise it with GP/family/work as appropriate. Many firms now have an independent counselling service who you can call to discuss issues such as this.