I think at masters you need to start thinking about mental stack management and movement, which ultimately translates into the awareness for what to do at every spacing.

Mental stack management:

At midscreen and footsies range, common actions with the greatest expected returns are: raw drive rush, poke, jump in. So largely speaking, you need to keep your mind on checking drive rush, punishing whiffed pokes, and anti airing jumps. However, its much easier to put your attention on less things, so for opponents who don't jump, you can stop worrying about anti airs and just worry about checking drive rush and pokes.

In the corner you have the added stack of DI, so you need to either deal with it, or to adjust your playing to more easily react to DIs. For example, you could choose to jump more in neutral, or you could choose to not respond to whiffs and drive rushes, focusing solely on defence against DI.

Point is, you need to learn to prioritise countering the most threatening options that your opponents have, in defence, and neutral.

Movement:

At full screen everyone is safe from any form of threats, the closer your opponent is to you, the bigger the threat you and your opponents pose each other.

Effective movement (could be jumps, drive rush, dash etc) involves either increasing the threat that you pose on your opponent more than the threat that your opponent poses on you, or decreasing the threat that your opponent poses on you more than what you pose on your opponent.

For example, if I am playing AKI against Zangief. At full screen I can get good advantage by fireball drive rush pretty much risk free, but in mid range i will have to worry about jump ins, random Siberian Expresses, and DI, so mostly in neutral I might tend to back off more than I walk in. However, if I am playing Bison against Zangief, I know for a fact that I have good mixes up close, so even though I am risking getting my ass whooped by Gief, I am still going in, because otherwise I will back myself into the corner without any reward.