Earlier quoted context omitted.
Because you did 5-8-5!
That restriction can't actually be adhered to in the right spirit outside the Japanese language, and isn't 100% adhered to even in that language. Counting syllables quickly on the fingertips before clicking Post
Basho's famous poem of a frog is a good example (this is my attempt at a 5-7-5 translation):
Into an old pond
a frog jumps in suddenly.
The sound of water.
But the key for anyone who has lived in the countryside is that frogs appear in the spring and their noise can be deafening. So to be aware of the sound of the frog's splash, one has to be at the start of spring, when the air is still cool and the world is just waking up from it's winter's rest. It creates a connection to the feeling of being lost in thought and suddenly awakening though the sudden sound of a splash of water. You get the feeling of renewal, rebirth and starting afresh. Or at least, this is what the poem says to me.
All this to say to the OP, I think if you try to think of a place or a situation that is iconic to you and then use a "seasonal" word to refer to that situation, then you will get more out of your haiku. For example, I really, really like juped's "before clicking Post" line because it evokes that feeling that we all know on HN -- a kind of shared experience.
And, yes, the syllables are not so important in my mind as long as it's close. It is said that more important than the syllables is that you have a break in the middle somewhere. So you should usually aim for 2 sentences/thoughts in your three lines with some kind of break of structure to indicate the division. In Basho's poem you get the "sound of water" that stands in contrast to the frog jumping in.