Subjunctive mood can be made difficult if you overthink it. I usually try to look at it as more of a wish or a proposal. “If this, then that”. The “then” part is usually implied, is how I was taught to think of it. Also, it’s not a concrete noun. In other words, it can often be left up for interpretation dependent upon the one feeling that mood. In the examples given above, one has a strong sense of what unhappiness & anger look like. Also, the “then” parts provided, such as “being there” and “saying something”are not wishes or proposals, but actual actions. what you’re looking for. The last sentence is clearly incorrect because “If you are going out later” is an action, not a mood.
That leaves only the first example. “If you are nice, (then) I will be your friend.” The idea of being “nice” is definitely a mood that is different for us all, that one cannot put a face upon, unlike unhappiness and anger.
I’m sorry if this isn’t coming across as well as I can see it in my own head, but if you’d like more help I can give it another go.
