The following paragraphs represent weak and strong examples of focus.
Weak Example:
When I first brought my cat home from the humane society she was a mangy, pitiful animal. It cost a lot to adopt her: forty dollars. And then I had to buy litter, a litterbox, food, and dishes for her to eat out of. Two days after she came home with me she got taken to the pound by the animal warden. There's a leash law for cats in Fort Collins. If they're not in your yard they have to be on a leash. Anyway, my cat is my best friend. I'm glad I got her. She sleeps under the covers with me when it's cold. Sometimes she meows a lot in the middle of the night and wakes me up, though.
Strong Example:
When I first brought my cat home from the Humane Society she was a mangy, pitiful animal. She was so thin that you could count her vertebrae just by looking at her. Apparently she was declawed by her previous owners, then abandoned or lost. Since she couldn't hunt, she nearly starved. Not only that, but she had an abscess on one hip. The vets at the Humane Society had drained it, but it was still scabby and without fur. She had a terrible cold, too. She was sneezing and sniffling and her meow was just a hoarse squeak. And she'd lost half her tail somewhere. Instead of tapering gracefully, it had a bony knob at the end.
Each of the Russian manned space exploration projects had specific major goals. For example, the Vostok project was designed to test whether or not human beings could survive and function in outer space. For another example, the Voshkhod project was intended to find out whether people could work in the weightless environment of space. One Voshkhod cosmonaut experimented with weightlessness by taking a "spacewalk." That is, he floated in a spacesuit outside his Voshkhod spacecraft, connected to it by a tether. The cosmonaut to do this was Alexei Leonov. Several weeks later, Leonov's spacewalk was followed by that of U.S. astronaut Ed White. Finally, the Soyuz project, with three cosmonauts, had goals of testing spacecraft and spaceflight skills so that people could fly long missions in Earth orbit.
This paragraph is generally good, but the sentence, Several weeks later, Leonov's spacewalk was followed by that of U.S. astronaut Ed White, does not have anything to do with the major goals of the various Russian space projects. That is, it is an "off-topic" sentence, so we can say that the paragraph somewhat lacks unity. In order to improve the paragraph, we should omit this sentence, even though it is historically accurate