I find learning several languages at once difficult. I know of people who speak several at once, but they often have a lot of time to practice (and can travel to several countries to use them). Time is a luxury not many people can afford, and certainly not for me. I prefer to focus on one language for a number of years to get the basics right, then continue learning on my own through books and other media. I have no need for more than 4 languages on a daily basis.

Find a language you have to use often, then there will be motivation to learn it. Otherwise, you will find yourself forgetting it after a few years.