My experience being bilingual

The number of the languages you can speak is never too big, I always believe in that. Speaking more than one language may not be a very practical skill, may not help you solve a specific problem. However, knowing another language means that you can communicate with another crowd of people, which may give you the chance to find the answer. One person can never know everything and different people are good at different things, so knowing different languages gives a chance to know many different people and gives you an access to countless new things. I have learned a lot about the American culture from my American friends.
On the other side, knowing another language may cause you trouble. Sometimes, you may speak another language while thinking in your mother tongue. In the first few years learning English, that condition was almost unavoidable. It is not a big deal when I am just speaking Chinglish or broken English. However, if I put English words in Chinese sequence (I cannot remember an exact example but it does happen sometime), it might have a totally opposite meaning. And speaking two languages at the same time will cause you mix the two languages together. Some people probably like that, however, I think that a language stands for a culture and only when you use a language long enough, you can feel and understand the culture in the language. When you mix the two languages together, you are seem using both of them, but you can touch the culture of neither.
I hope that I can have the time to learn a language till I can use it as well as my mother tongue and during that period of time, I will not be unfamiliar with my mother tongue. However, it will always be a dream. The benefits and difficulties of being bilingual can never be measured and compared clearly.