Even clever people may fail if they work by fits and starts. Take, for example, a clever student who is lazy. He works only now and then. He is never regular at his studies. He might fail in his exam. His failure is due to the fact that he did not work slowly and steadily.
The truth of the proverb is illustrated by the story of the hare and the tortoise. The hare challenged the tortoise to a race. He was sure he would succeed because he could run much faster. He ran ahead and the tortoise was left far behind. So the hare decided to rest and have nap. The tortoise went slowly and steadily on. The hare woke up after his nap. He found that the tortoise was very near the goal. He leapt forward but it was of no use. The tortoise had won the race, because it had moved slowly and steadily.
Nothing is gained by being hasty and careless. It is better to be slow and careful in one's work. Those who do things hastily sometimes make many mistakes. Then much time is lost as the work has to be done all over again. It is better to be slow and steady. To conclude we might say that what one needs to succeed is the ability to work hard and to do one's work with patience and perseverance.