As I pointed out in class, a common mistake you often make when speaking and writing in English is using the infinitive of purpose in a wrong way, that is to say, trying to use 'for' instead of a 'to-infinitive' when you want to express purpose.
- He's looking for a part time job to save some money.
- She wakes up early to be on time for work.
- They exercise regularly not to get fat.
Joke, Explanation and Exercises