Questions

• How important do you think motivation is for success in language learning, compared to, for example language aptitude?

I think it's very important because you learn faster and you enjoy what are you learning, motivation can be part of the process of learning, in this case of second language is something that you want to learn, you search information about it and learn by every possible way.
and learning aptitude is the capacity to learn a new language but not always is what you really want to know and you don't enjoy it.

• How important is people's past success in language learning for their motivation to learn in the present and future?

Sometimes is very important, but not always because some students may have a good relationship with 2 language and he will be more open to keep learning, but if the student had a bad experience, that doesn't mean that he won't be able to learn it.