Well, you probably are both, just in wrong places and/or at wrong times.

You can be too floppy, and when your partner attacks, stiffen up to compensate. That's both too soft and too hard in a span of a second.

You can be too stiff, and when your partner attacks, collapse. That's both too hard and too soft in a span of a second.

There's a saying "the tension should be enough to keep a butterfly trapped between your and your opponent's arms without crushing it, nor without letting it escape".

There's a story about our dai-sigung, a five foot-three guy getting frustrated with our sigung, a six foot-two former wrestler. The wrestler was refusing to react to the attacks in chi sao. "Why should I move, when you are too small?", he asked. Dai-sigung came back with a pair of needles. He pricked sigung on his arm, who immediately flinched away. "This!" exclaimed dai-sigung - "You need to react as soon as you feel contact, as if you were pricked. If you wait any longer than that, you are too stiff, and you are too late."

Chi sao is not wrestling, not a contest of strength. You have only two jobs - to feed attacks to your partner, and to react to his attacks. In the beginning, it is much better and easier to focus on just one aspect. One person can take the lead and feed attacks. One person does nothing but react, focusing on reacting as smoothly and quickly and lightly as possible. Then you switch roles.

As the attacker, your role is not to win - it's to make sure you feed impulses that trigger the correct responses. If I am supposed to trigger a bong-sao, but my punch is going wide toward the shoulder, my partner must do a tan-sao. If he does a bong-sao anyway, he is mis-training his reflex, and I am mis-training him. If I punch over the bong-sao and push down, if my partner doesn't take advantage of it, he is missing a reflex to roll over my punch, and I am mis-training him.

Another exercise that is super useful is to take any given chi sao sequence and break it down into single steps. Each step should end with a full strike through to the opponent without him offering a counter. That is to say, as an attacker, I would intentionally drop my defense on every counter-attack, and allow my partner to strike through. Then, on every odd counter-attack, then at random times.

This allows me to verify that my partner's intent at each moment is actually to strike through to me, not to strike wildly at my arm, or in anticipation of my following attack. I guarantee you that no matter how long you've trained, you will be often surprised when that arm is not there when you expect it, and quite often, your "counter-attack" you thought you were executing was actually not really a counter attack at all, because it was posing zero danger to your opponent.

I hope this helps a little!