Exercise?

It wasn't easy...doing sit-up after a very long rest. I tried my very best. Starting last Friday, 100x in the evening. Didn't manage to do in the morning though due to times constraint.
Someone told me it is not good to do sit up at my age. Wow!!! it does makes me feel like I'm ancient. It is for good intention, I believe. To avoid any injuries. True but it made me feel like I want to hide under the duvet and never bother to exercise anymore at all.
Naaahhh!!! I can never hide under the duvet. Got too many things to do. The kids, the housechores, the officeworks, my life and the lists go on and on.