I've sort of been a language ping-pong ball myself. At one point in my life I was learning three languages at once. This was inflicted upon as criteria for the first major I attempted at college, later having switched. I can say that for me, language learning is best when one can focus upon a single language. I can not tell you which language to chose. To me language learning is a very different type of learning. Because we communicate with language, language is a vehicle for the transmission of culture. Language also frames thought. For this reason, I have always found language learning very enriching, as through language learning one is able to create new pathways for our thought patterns. Learning more than one language can be end up being very confusing no matter what.