BW Online's Entrepreneur Journal has an article called "Custom-building a Life." Inside, restauranteur Jeff Weinstein talks about his struggles to find balance between his successful business and his family. He tried to make his work and family responsibilities fit neatly into a schedule, but as small business owners know, that is not always possible. After all, problems can arise outside of 9-to-5, and often you are the one who needs to solve them.
While I am certainly no poster child for good boundaries, I'd like to offer the following suggestions. First, of course, is to know when to delegate, and then do it. Entrepreneurs are so comfortable relying on themselves that they often mistakenly believe that they need to do everything personally. Instead, they need to recognize which tasks (most small tasks and some large ones) can be delegated to an employee or business partner. The measure is not whether someone else can do it exactly as you would, but whether they can do it competently. If they can, then stand back and let them do it. You may be surprised at their competency and innovation. The best part is, you won't be spending your Valentines Day dinner dealing with work problems.
A second, and related, suggestion is to recognize when something is an emergency. Part of this is learning to stick to a schedule. If you tell yourself that you leave work behind at 5:00 (or whenever you set your work hours), then that does not mean that you cannot handle emergencies as they arise. But it does mean that you should only be dealing with emergencies after 5:00. This is by far my biggest work-life balance issue, so I understand that your brain will not shut down at 5:00. But there are ways that you can minimize how much your work cuts into your personal time. If you get a brilliant idea during "CSI," then jot it down in a notebook. And leave it at that. You can spend time developing your brilliant idea tomorrow at work.
If your problem is that your work invades your personal time because you simply don't have enough time during the workday, then you need to deal with that issue. Perhaps you need to delegate (see above). Or perhaps you need to work on managing time better (that topic is way too big for this little blog post). If you can't delegate because you have no one to delegate to, then find help - whether it's relying on professionals to assist, or hiring a new employee.
I'm sure you can think of many reasons why you can't utilize this advice, and that's okay. But it's your life that your work is invading, and only you can put a value on that. And maybe that's where you need to begin.