Holding abs tight while working out


I've been working out intermittently, but was never regular. I just started with the 5 day challenge and today was Day 5!! I feel so good about myself.

Most of the workouts ask us to hold our abs tight while doing any kind of exercise. I've been unable to do that naturally and sometimes I just focus on the workout rather than my abs. I'm hoping I would get that as I start working out more and more. Is that ok or do I really have to focus on my abs too to gain the maximum benefit?