Sleep finally came at 8 a.m. on Monday, after toothache all night, or should I say gum ache. I should have taken painkillers earlier but kept thinking it would pass, as it wasn't really that bad, but eventually I gave in and managed five hours of sleep. Sleep and rest are vital in my line of work. Someone once did research that showed that a singer uses up the same amount of energy singing a major role as a marathon runner. I can well believe it, and many of the same muscles are used, too. I have had one singing teacher since I was 18 years old, and this makes me quite rare among professional singers. His name is Joseph Ward, and I truly believe I would not be here today but for him. He knew how to teach a big voice like mine and how to be patient and wait until the voice and my body were ready to produce the sounds he believed I would be able to. You cannot force a voice to do things, though some people do, and bigger voices tend to take longer to develop than smaller ones.

Keeping healthy is something a singer tries to do at all costs. A cold is a nuisance for anyone, but for a singer it can mean the difference between getting paid and not. Most singers are only paid for performances and not for rehearsals, which can mean if you get sick during the shows you can lose a lot of money. I try to stay as healthy as I can, and if I feel I might be getting sick, I take the usual precautions of drinking water and taking zinc and vitamin C. However, there are times when there is nothing you can do but hope that it won't affect the voice. I have sung performances with bad colds and sore throats, and as long as the vocal cords are not infected, then you will not do any harm to the voice. Around 10 years ago I was diagnosed with a lump on my thyroid and was told that there was a good chance it was cancerous. I found the best surgeon I could, who was in London at St. Bartholomew's Hospital, and put myself in his hands. As I went into the operating theater I told him I wanted to come out of the surgery able to sing the same notes as when I went in. He said he would do his best, but his first job was to save my life. The lump was not cancerous, and he did a wonderful job, saved my voice and left me with a very impressive scar in the middle of my neck. If I am very sick and think I cannot do my best work, then I will cancel. I do this very rarely, despite what has been written in some of the press. I think it is important to give the audience as good a performance as you can every time you step out in front of them, but if I think I cannot reach a certain level, I will not sing. It's always disappointing for any singer to cancel and for some of the audience, too. It always amazes me what some people will say or write to singers sometimes. I once received unsigned hate mail for "canceling a performance on a whim," whereas I had actually been violently ill. You learn to develop a thick skin in this business.

Having finally got a few hours' sleep, the day was made up of doing errands and catching up on mail and messages. I did a little shopping and bought a new concert dress for a performance next month in Berlin. The concert came up at the last minute, and I don't travel with evening clothes unless I know I am going to need them. Packing for three months away is difficult enough without taking things you may not need. Luckily, both my husband and I don't really feel the cold, so we don't need huge sweaters and coats to take up the space. We would much rather have space for books and CDs … a mixture of classical music and rock music.

I also managed to do lots of laundry, which is something I actually enjoy. I can't say the same for the ironing that follows, but my husband doesn't mind that, so in that regard we are a perfect match. Sadly, my beloved Seattle Mariners lost to the Yankees, and their incredible season is over. I have often thought how similar a professional sports person is to a performer. They hone a talent and make a living from it, they have to "perform" at a given moment … hit a high C or a home run … and they have a lot of people watching them who think they could do better and offer "advice." It's hard but also wonderful to be able to make a living from something that most people only have as a hobby.

I am hoping that sleep will be long and deep tonight, as I have a performance of Norma tomorrow. I wonder if any of the Mariners players relax with opera, as I relax with baseball?