Starting as a designer with a fresh psychology degree and little design skills whatsoever (but a huge passion for design) I stuck to minimalistic designs even when it was not fancy, way before it was cool. In my own time I learned how to play this card right so that my designs didn't seem boring and blank, but rather sophisticated and elegant.
It is always best to stick to what you feel true or more comfortable with, this way you will invest enough duende to your designs. http://en.wikipedia.org/wiki/Duende_%28art%29
And duende is the only thing that creates an emotional design, something users can relate to. Whatever has duende, should pay off.
So whatever you like, be it maximalistic layered designs or stylishly minimal ones, follow it. You will need a success criteria for your own work anyway, so use your own aesthetic standards to decide what is good, what is working. In other words, be your own number one user. When you feel it's time to make the design more decorated, then it probably is.
What is cool about times we live in, however, that this is the age of minimal design, and you can be trendy while being true to yourself. And the limit of how minimal the design can be before it starts feel dismally empty have been pushed significantly just recently by the Material Design concept and all the new technologies that are conceptually in line with it.
How to surf minimal design in a cool way and feel more secure about it:
Material Design Guidelines by Google
I also wrote a long answer on a related question about Minimal Design some time ago, so it might be something of interest. https://ux.stackexchange.com/a/69982/57766