Writers are often advised to write about what they know about, so writing from personal experience can be a good way to ensure that there is authenticity to your novel. However, this doesn't mean that if you're a teacher you have to write about being a teacher. I work in a bank but much prefer to write horror or sci fi stories where bankers and banks are completely absent. I can still, however, draw upon my own experiences in life (and sometimes from work) when writing a novel or short story, even if the setting is far divorced from my reality and the characters purely fictional. For example, if one of my characters is a lovesick vampire, then maybe I can draw upon a personal experience of having once been single to draw either pathos or comedic value from the scene.
Having said this, it may be that you have a particular event in mind that you have lived through and which you feel would be suitable for a novel. If that is the case, then there are several factors that you need to take into consideration. At a basic level, you need to ask yourself whether the story you're intending to tell will be of interest to other people? It may be a story and event that is deeply important to you but if it's not going to ignite the interest of strangers, then it's probably not worth expending the energy on. You should think about what things make your story particularly noteworthy? An odyssey across North America on bicycle might be a great achievement but that, on its own, may not make your novel jump off the shelf. On the other hand, I saw a documentary recently about two ladies from the UK who did such a trip. They were both about to turn 70 and were doing the trip to raise money for a cancer charity. The fact that the ladies were of an age when most of us would be taking life easy and the fact that there was a charity angle had obviously caught the attention of a TV channel. Marketing professionals often talk about the importance of having an USP (Unique selling point) and this holds true for novelists as well!
If you have reviewed your novel concept and have decided that it does have potential, then you need to decide whether you are going to use the names of the real-life protagonists or whether you are going to preserve anonymity?! If the real life event that you're going to base your novel on has messy or unhappy consequences for individuals, then you may want to veer away from the subject or make sure that you disguise the characters and event to a reasonable extent. For example, a novel that centres upon a fling that a married man had with a woman ten years ago may not be welcomed by those individuals or their families. Additionally, one always has to tread a careful line to avoid the potential of being sued for defamation!
For most writers, however, the bulk of our writing will incorporate personal experiences in a less direct fashion. We will meld thoughts and experiences that we have had into fictional characters and storylines and, hopefully, the fact that our writing is supported by personal experience will add extra credibility and realism to it. Finally, I think it's worth adding that personal life experience is an invaluable asset for any writer. Often, writers produce much higher quality when they are in their thirties, forties, fifties, etc, than when they were teenagers. In part this may be a maturing of writing style but it's also due to the fact that it's much easier to write authentically about various life experiences if you have actually gone through the excitement or trauma of them. So next time you experience or witness something that is emotionally powerful, you can tell yourself that you're going to turn it into an excellent scene in your next novel or short story!