You can feel it.. a little. It's a nice feeling if you avoided something that would have hit you.
When you leave a gap open too long, they'll try to attack, normally with 2A/2B/2C, Hisui's j2c is great to do during that situation. ^^
Imagine something like this:
You and your opponent and sitting next to each other blocking. If you threw out an attack half a second before he did, you get a counter and you can combo from there, and if he attacked before you did, then you're the one being combo'ed. If you can grab them before their attack comes out, then you get the grab. Just use good judgment or gamble a bit. Every time you're tickthrowing, you're gambling a small bit by leaving an opening, but it's pretty useful since your opponent can just block all the time and it's easier than having to continue your pressure until they mess up or guess wrong, and it makes your opponent stop shielding as often in response to a dash-in.