In life as in Aikido, one must have timing. A good Aikidoist will have average timing, but a great Aikidoist will have phenomenal timing. But, what is timing?
Timing is something that is difficult to explain. Google defines it as, "The choice, judgment, or control of when something should be done." That definition is something that one can understand but still not know. Timing can be thought of as just the right point when something extraordinary can happen. A good metaphor might be the moment when darkness turns into light or when light changes into darkness. When the day changes over, there is this place and within that place exists a subtle moment when it is neither dark nor light. If one is aware then one can catch a glimpse of its immense beauty. To the uninformed, the day just became night or the night just became day.
Every person has some sense of timing - it is innate. How do I know that? Does your heart beat? Then you have timing.
It doesn't matter if one is studying acting, Aikido or driving - timing is important. To develop that sense of timing requires training. Lots and lots of training. In training, one develops their body first and then their mind second and with these developments comes a sense of awareness. This awareness enables one to almost see the timing, but it is a feeling thing more than a seeing thing. Seeing it is too late. Just as in when the day turns over, you feel it before you see it and then it is gone. In sports it is called being in the zone. This "zone" type awareness enables the athlete to almost control the moment because their awareness creates this sense of vastness. Athletes report things like the ball being 10x larger or the goal being infinitely bigger enabling them to score with ease.
When one's awareness is developed then one is able to seize the moment and that is why people often say, "I caught the timing."