People always seem to be concerned with wasting time, as if it's some sort of currency or something that can be traded. Time isn't some physical commodity that can be thrown away or exchanged for something of greater value. Time holds different meaning and value for every single individual, it isn't something that can be measured absolutely like money. 'Spend your time wisely' is a rather superficial way to look at life in my opinion. In the end we all die, and then time and how long you lived or how you spent that time in meaningless anyways.
Please don't take this the wrong way, the fact we die isn't meant to frighten or scare you, it's to illuminate the fact that in the end how we spent our time or how wisely doesn't matter in the least. It's for you to decide what goals to set and what actions to take. It doesn't matter how you spend your time, for in the end we all obtain everything and nothing in exactly the same quantity.