In life, for doing something one needs encouragement and incentives. Incentives can be tangible like monetary benefits or some intangible benefits like love, affection, good will etc. I learnt English, German (I could not learn properly) and Hindi along with my mother tongue, Assamese for tangible benefits, like better prospect of getting good jobs. In effect, command in English grammar helped me to get this job and this job helped me to have a beautiful wife from a good family.
The rest of the languages; Bengali, Gujarati, Punjabi, Nepali, Sanskrit, Oriya and Marathi, which I knew at different levels; were learnt due to different incentives. Some were learnt due to some tangible compulsions and some were learnt for intangible benefits. For example, I learnt Sanskrit, because I was told by my seniors, it was easy to score marks in Sanskrit. However, I could not score good marks in Sanskrit compared to other subjects.