〜ようにする vs 〜ようと思う

Question

I'm wondering about the difference between 〜ようにする vs 〜ようと思う, which both express intention. Here's an example sentence from A Dictionary of Basic Japanese Grammar (pg 562).

私は毎日運動するようにする。

I'll make sure that I do exercises everyday.

Changing this to the volitional form 〜ようと思う, and my best translation:

私は毎日運動しようと思う。

I think I will exercise everyday.

Do the English translations capture the nuance in both sentences (the former seems to express a higher level of intention)? If not, what is the difference?

Answer 1

I think the key difference between two versions is that the former is passive and somewhat more apologetic and the latter is more proactive.

For example, if a doctor tells you to exercise regularly, you'd tell him 毎日運動するようにします. If a mother scolds you that your report card was horrible, you'd say 毎日勉強するようにするから

私は毎日運動しようと思う has a feel that you planned it, and you are initiating that change. It feels more positive.

In both cases, I think your translation is spot on.

Answer 2

毎日運動する、毎日運動しなければ、毎日運動するつもりである、etc. would be showing clear intent to exercise more.

毎日運動するようにする is kind of wishy-washy. I'm gonna try to do some exercise (although I really don't really have that much passion for it). It is not 'make sure that'

I think your translation for 毎日運動しようと思う　would be fine. I think, though, that it would be more common to say 毎日運動しようと思っています。 'I'm thinking about (planning on) exercising everyday.'

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