Yeah this is really just about comfort and familiarity. It’s one thing to know what you’re doing in training, in a controlled environment, trying to learn and apply one concept or technique at a time. You’re “choking” because your situation recognition is bad right now. That will improve with experience.
Trying to remember how and when to apply all of that in the relatively chaotic conditions of an actual match is an entirely separate beast. There is no easy answer other than to “play more.” Over time you’ll start to become more comfortable at recognizing situations in actual matches and focusing only on the details that are actually important at any given time. The ‘signal to noise’ ratio will become much better for you as you start to appreciate what is actually the ‘signal’ (important information) and what is ‘noise’ (everything else you’re thinking about or paying attention to), and that can change in an instant in games where timings down to a fraction of a second can make a difference.
The other piece of advice I’ll give, though, is this:
Focus on learning, not winning.
Winning is good, but don’t put pressure on yourself to win. You’re new to the game - don’t be surprised if people who’ve been playing the SF series for 20 years are kicking your ass, and don’t let it get in your head. Instead of focusing on “damnit, I just keep losing!” you need to focus on “how did my opponent beat me? what could I have done better in that round? what am I learning from this?”
As soon as you stop caring about winning, and start thinking more about being patient and learning, I think you’ll both a) start enjoying the game a lot more, and b) stop choking as much because you aren’t paralyzed by a fear of losing/the desire to win, but instead understand that you’re going to get beat up again and again, and that each of those losses is an opportunity to learn and get better.
The truth about Street Fighter that most rookies may not grasp is this - everyone, everyone, had their ass totally kicked, again and again, when they were first starting to learn the game. Daigo didn’t just pick up Street Fighter and dominate from day 1 - I’m sure he took more losses than he’d care to admit in the process of becoming the player he is today.
You’re new to the game. You’re not supposed to know what to do. You’re supposed to lose. Embrace that, and focus on learning how you are losing, and applying that analysis to improving yourself in the future.