The key to your self-defense in any style can be unlocked by competently studying your forms. It is not enough to be able to flawlessly perform movements if you don't know what the movements represent. You must also be careful of common pitfalls: take Taeguek 1, for example. The first movement is a turn to the left and low block. Many instructors teach this as a block to an incoming roundhouse kick from the left. If this is the explanation you're given, then, your instructor does not know what s/he is doing.
Each movement presupposes you've already been attacked; in the preceding example, it presupposes you're about to be attacked. Aside from the absurdity that anyone would wait until the last second to turn and block what will be expected to be a kick, we must think that the attack could be anything. It is much better and open-minded to consider an attack that has already occurred, and your first response is to turn to the left. There are a boat-load of possible scenarios - I can think of a dozen at the top of my head.
Next, consider some of the odd movements, like the spearhand (2nd movement in Taeguek 4), which requires the left palm down as the right hand extends to a spearhand. Did anyone ever tell you that the spearhand was a strike to the solar plexus? Hopefully, your BS-o-meter is ringing off the hook. The fact that your left hand is assisting in some way should give a hint. Why is it absurd? Because you would be placing your face and trunk in such close proximity to your opponent, and you have not given any protection to your face and trunk: a recipe for disaster. (Answer: the "spearhand" in this case is a throw. The giveaway? That's the double knifehand block that precedes it, which isn't blocking anything. The inside hand on the sternum was grabbed, you turn that grabbed hand palm up while pushing the opponent's head away from you - that's (one) purpose of a double knifehand "strike". The step in to the spearhand is the elbow lock (left palm down) and throw (the thrust of the spearhand throws the opponent).
To unlock all of this, you need competent instruction. There are many books and prominent stylists out there, like Iain Abernethy. They're great for giving you ideas, but you need hands-on practice. You need a mat. And you need someone to explain the "rules" of learning your forms.
To give you a start in the right direction, I recommend the book "The Way of Kata", by Lawrence Kane and Kris Wilder. They explain forms from a Karate perspective, but, the concepts easily adapt to Taekwondo.
I also recommend YouTube channel by Iain Abernethy, and another channel by John Burke. There are several others.
Watch, read, memorize. Then get practical hands-on practice on the mat from a competent instructor.
You will learn that forms teach us many things: technique, balance, striking, blocking, parrying, throwing, falling, breath control, pressure points, joint breaking, locks, pins, adaptation to pain... and more.
Above all, be open minded about the instruction you read about, watch, and experience. There are a dozen ways each technique can be applied, there are no right or wrong scenarios - as long as they make sense.
Some people recommend cross-training. If your instruction is competent, there should never be a reason to cross-train. Your style contains all that you need to learn. If your instructor is a boob, then, of course you can either cross-train or change schools. Otherwise, pay attention to your instructors.