Learning a foreign language takes time and dedication. The reasons below may help to convince you to take the plunge, if such persuasion is needed. Some reasons are practical, some aspirational, some intellectual and others sentimental, but whatever your reasons, having a clear idea of why you're learning a language can help to motivate you in your studies.

Kolik jazyků znáš, tolikrát jsi člověkem.
You live a new life for every new language you speak.
If you know only one language, you live only once.
(Czech proverb)

Emigration

When you move to a different country or region, learning the local language will help you to communicate and integrate with the local community. Even if many of the locals speak your language, for example if your L1 is English and you move to the Netherlands, it's still worth your while learning the local language. Doing so will demonstrate your interest in and commitment to the new country.

Family and friends

If your partner, in-laws, relatives or friends speak a different language, learning that language will help you to communicate with them. It will also give you a better understanding of their culture and way of thinking.

Work

If your work involves regular contact with speakers of foreign languages, being able to talk to them in their own languages will help you to communicate with them. It may also help you to make sales and to negotiate and secure contracts. Knowledge of foreign languages may also increase your chances of finding a new job, getting a promotion or a transfer overseas, or of going on foreign business trips.

Study or research

You may find that information about subjects you're interested in is published mainly in a foreign language. Learning that language will give you access to the material and enable you to communicate with fellow students and researchers in the field.

Language is the archives of history.
(Ralph Waldo Emerson)

Travel

Many English speakers seem to believe that wherever you go on holiday you can get by speaking English, so there's no point in learning any other languages. If people don't understand you all you have to do is speak slowly and turn up the volume. You can more or less get away with this, as long as you stick to popular tourist resorts and hotels where you can usually find someone who speaks English. However, if you want to venture beyond such places, to get to know the locals, to read signs, menus, etc, knowing the local language is necessary.

Food

Perhaps you enjoy the food and/or drink of a particular country or region and make regular trips there, or the recipe books you want to use are only available in a foreign language

Linguistic interest

Maybe you're interested in linguistic aspects of a particular language and decide to learn it in order to understand them better.

Challenging yourself

Maybe you enjoy the challenge of learning foreign languages or of learning a particularly difficult language.

Showing respect (from Nicole Signer)

I believe that when somebody at least tries to learn the language of the country they are visiting it shows a lot of respect. People really appreciate it.