I have a 16 month old daughter who most of the time is pretty wonderful, but like all toddlers can be very naughty and challenging.
A friend suggested a book called Toddler Taming by Dr Christopher Green and it has been wonderful. I was lucky enough to pick up a pre-loved copy at the markets for $5.
It helps you to understand why your toddler is doing the things he / she is, and allows you to know it is normal and that no, you are not going crazy...
Goodluck with your toddlers.