Question about は particle in ようにする

[Jonapedia]

@haughtygee

Though I’m afraid my interpretation can only go so far and I’ll have to grind grammar references and read some more to actually understand the nuance.

You’ll work it out eventually with experience. But if you want some ideas on は vs が to keep in mind/help you along when you’re confused, you could try looking at this (not my ideas – I just translated an article that was written in Japanese):

@Jonapedia

Using「は」and「が」Appropriately

The things that have been constructed as explanations of means of using the particles「は」and「が」appropriately have been classified into five categories and summarised by Noda Hisashi.
（1）The method of discerning appropriate usage based on whether the information is new or old
In conversation and from context, the standard is that if the noun in the nominative case is unknown (= new information), one expresses that using「が」; if it is known (= old information), one expresses it using「は」.
・鈴木さんは校長です。Suzuki-san is the principal.（Because Suzuki-san is ‘known’, one expresses that by attaching「 は」.）
・鈴木さんが校長です。Suzuki-san is the principal.（Because who the principal is ‘unknown’, one expresses that by attaching「が」to「鈴木さん」.）
[Note: I may have over-interpreted some sentences in this first section in order to preserve the sense of 表す, but the truth is that I don’t think there’s any one specific thing – indicated by ‘that’ or ‘it’ in my translation – to be expressed. Rather, the idea is that one should speak/express one’s thoughts using the appropriate particle in each case.]
（2）The method of discerning appropriate usage based on whether the sentence is phenomenological or evaluative
A sentence that describes a phenomenon as is, without adding the speaker’s subjective assessment, is called a ‘phenomenological sentence’, and「が」is attached to the subject. In contrast to this, a sentence in which the speaker adds subjective assessments to a phenomenon and describes it is called an ‘evaluative sentence’, and「は」is attached to the subject. This is a method of discerning appropriate usage on the basis of the above.
・（looking at a dog before one’s eyes）犬が寝そべっている。The dog is sleeping flopped down on its belly.（phenomenological sentence）
・（pointing at an umbrella that seems to have been taken by someone else by mistake）それは私の傘です。That is my umbrella.（evaluative sentence）
（3）The method of discerning appropriate usage based on the point up to which the subject is relevant – up to the end of the sentence, or only within a single phrase
When the subject is relevant up to the end of the sentence, one uses「は」; when it is only relevant within a single phrase, one uses「が」. This method works on that basis.
・父が晩酌をするとき、つきあう。I keep my father company when he drinks during dinner.
・父は晩酌をするとき、冷や奴を食べる。When my father drinks during dinner, he eats chilled tofu.
（4）The method of discerning appropriate usage based on whether or not the nominative case expresses a contrastive meaning or an exclusive meaning
If the nominative case has, relative to some noun of the same type that does not appear in the sentence, a comparative meaning similar to ‘by comparison, it is […]’, then「は」is used（contrastive「は」）; when it has an exclusive meaning similar to ‘only this is […]’, then「が」is used（exclusive「が」／「が」of generalisation）. Discerning of appropriate usage is performed on this basis.
・犬は好きだが、猫は嫌いだ。While I like dogs, I dislike cats.（expresses a contrastive meaning）
・ 私が責任者だ。I am the person in charge.（expresses that among those present here, it is not someone else, but ‘I’ who is the person in charge）
（5）The method of discerning appropriate usage based on whether the sentence designates something (指定文) or formulates a proposition (措定文)
The predicate of「貴乃花は横綱だ」=‘Takanohana is the yokozuna’ expresses the nature of the noun that acts as the subject, and the sentence cannot be reformulated as「横綱が貴乃花だ」. Such sentences are called「措定文」, and「は」is used in such sentences. In contrast,「鈴木さんはあの人だ」=‘Suzuki-san is that person’ expresses that the noun in the predicate and the noun that acts as the subject are the same thing, and it is possible to reformulate is as「あの人が鈴木さんだ」. Such sentences are called「指定文」or「同定文」(‘statements of identification’), and in such sentences,「は」and「が」can both be used.
・地球は、太陽系の惑星だ。The Earth is a planet of the solar system.（措定文）
・あの人の趣味は、勉強だ。That person’s hobby is studying.（指定文）

No need to memorise these things, especially because they don’t always come naturally, but I found that asking myself which nuance/difference I was seeing helped me early on as a learner.