Always remember that there are good days and there are bad days and sometimes you can't tell the difference until you start training. Contrary to popular belief, sleep and eating well is not overrated. Not in the slightest. Don't forget to breathe, it helps you with your heartbeats.
Like Ironman4U said, create a plan and stick to it. It may not always work, but if you stay focused and relaxed, it'll all end up just fine. Oh, and just because it is raining, doesn't mean one has to cry about it, lol, jk. To conclude, be careful doing a lower train brick (bike/run), you could injure yourself if you jump into it too quick.
Best of luck, and remember that getting to the starting line is usually a lot harder than getting to the finish.