Is it stressful to work in a law firm?

If you are an associate you will have to handle the substantive work. You will have to keep your productivity high. Billable hours are the bane of lawyers existence. Even people who work on contingency fees  or  corporate have   goals they must meet to remain employed. You will have clients to please sometimes with unpalatable advice; sometimes you never see the client, only the contact lawyer ( rain maker in US parlance) presents your work. You have to please the judges if that is your field. All of this in areas where you may or may not have any idea what you are doing.

The hours are long. Tempers run short. Privileged Characters ( adult version of  entitled brats) are rampant. Someone else is always , always, trying to market the client away from you, both in your firm and outside of it.That means politics in teh office can be fierce.

If you are a principal/ owner/partner in a firm, you have the added pressure of making sure there are enough clients/cases/income to keep the business running. A law firm is most definitely a business. You do all this while juggling the problems caused by the aforementioned Privileged Characters who think that the rules don't apply to them.

I started doing this in 1974. Most of my war stories are not printable

Morever, When you are representing clients, regardless of the area in which you are representing them, you incur a high level of responsibility. It doesn't matter if you are an attorney, a paralegal, a secretary, the receptionist, or the guy working in the mail room. You are a link in a chain that must be properly managed to make sure the client is receiving proper representation. There are deadlines to meet, rules you must know (staff must follow certain attorney ethics rules) and stressed out attorneys to deal with. All work must be performed properly because mistakes can lead to damage to a client's representation, which can lead to a malpractice lawsuit. Ethical violations can lead to a lawyer being called before the ethics board.

Never mind, you might be dealing with clients, depending on your role. Sometimes the clients are upset and will take it out on anyone they happen to talk to. Frequently, this is the secretary or the paralegal. This is especially the case if you are dealing with consumer law, i.e. where you are representing an individual as opposed to a business, and litigation has commenced or will. Litigation is stressful for everyone, but especially the client.

Some areas of practice are more stressful than others. Some firms are more stressful than others. Some bosses are more stressful than others. In this way, law is no different from any other job. But there is a lot that can go wrong and even minor mistakes can have serious consequences.