(Disclaimer: don't just buy a dog because I told you to. And if you are going to buy a dog, make sure you get it from a RSPCA approved organisation).
Get Some Sun
This is all about moderation: if you stay all day in the sun (especially in Australia) you will end up looking like a cooked lobster and that doesn't make anyone happy (least of all the lobster). However, if you spend a short amount of time in the sun each day, your body will produce endorphins (the happy hormone) and there is also a link between sunshine and melatonin and serotonin, hormones that help us sleep. Who doesn't feel happy after a good night's sleep?
Here's a hint: don't wear your sunglasses otherwise your body doesn't realise it's in the sun and you don't get the full benefit.