If you're not prepared for your first flat, you'll find it very annoying. Learn how to fix it, and always carry the gear to do it. Generally, you take the wheel off, remove the tube, remove the tire, inspect the tire carefully, as it may have the puncturing shard of glass still embedded, install your spare tube, put everything back together, and pump the tire up. I carry a patch kit in case I get two flats, but I can't remember the last time I patched a tube on the road. I have several spare tubes and make sure my tool bag has a good tube in it. I toss my punctured tubes into a pile and every so often patch them all at once. This way, my glue doesn't dry out.
I run my headlight and taillight day or night. Maybe it doesn't make me safer, and maybe it does, but it doesn't increase risk. Be sure your headlight is not pointed so high that it goes into people's eyes.
Learn what clothes work for each range of temperatures. You may need different clothes than you would need while walking. I need less on my trunk but more on my hands and neck.
You'll be surprised at how you can toughen up to inclement weather with a little practice. But if you find some days too unpleasant, that's fine, too. Not many people really are forced to ride a bike when they would rather not. When the surface is too slippery or when it's too cold and windy, I don't ride.
I keep a complete set of clothes at work in case I get drenched on the way in. I have to use them about twice a year.
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Inisfallen's advice is excellent.