Every time you talk of a character being "sad" or "happy," or even "miserable" or "ecstatic," cut it. Chop it right out; you don't need it. It's not driving your story ahead or giving it any momentum. These things can and should be made clear in other ways. Unless it's in dialogue, it needs to be scrapped. In other words, another character could ask, "Why are you so sad?" but the character at hand would never explore their world confined by the titles given to emotions. After all, "sad" or "miserable" are just words. If we called them "gobbledegook," it'd mean the same thing. These terms have no resonance emotionally. Even "she glanced over and grinned," is a good start for your first draft. Anything that moves away from, "she was happy" is a step in the right direction. This will evolve and grow over the course of your writing; right now, you just need something to hold it together. This is just laying the foundation of your story. Its purpose is just to be cohesive and hold the story together. You'll change everything later once you have the story pieced together. Why did she glance over and grin? What was she thinking to herself? Was she thinking that the boy in the corner was kind of cute? Did he remind her of anyone? What was the motivation for the emotion? Explore the techniques discussed above. Painting an image through dialogue, subtext, body language, and the senses will create a 360-degree picture for your audience to feel fully engrossed in the story. Instead of "she was happy," your audience will actually know how she feels. They won't drive your story forward -- they're too trite to do so.  Few things are less communicative than "I was so happy I could die" or "I felt my world falling apart."  If your character's that happy, have her spontaneously hug someone and then laugh aloud.  If you were that upset, say what happened.  People can understand the emotional impact of any major event; if you describe it, they'll know what it does to the people involved.  Never end a clear, intimate description...

How would you rephrase that briefly using Indonesian?
Baca kali karya Anda dan buang setiap kata yang mengacu kepada emosi. Untuk draf pertama, ganti dengan aksi atau imaji yang simpel. Untuk draf kedua Anda, coba untuk menulis lebih detail. Hindari hal dan kalimat yang klise. Jangan melenceng ke mana-mana. Saat Anda nyaris selesai, coba rasakan emosi yang Anda tulis.