Mr. Lamb was happy in spite of his disability because of multiple reasons.

a) Acceptance of his disability:
Mr. Lamb had accepted his disability and learned to live with it. He did not let his disability define him or limit his happiness. Instead, he embraced his circumstances and found joy in the things he could do. This acceptance allowed him to focus on the positive aspects of his life rather than dwelling on his limitations.

b) Wisdom:
Mr. Lamb's wisdom played a significant role in his happiness. With age and experience, he had gained a deeper understanding of life and learned to appreciate the small joys. His wisdom helped him to maintain a positive outlook and find happiness in the simplest of things. Instead of lamenting over what he couldn't do, he cherished what he could, which contributed to his overall happiness.

c) Aging:
As Mr. Lamb had grown old, he had developed a sense of contentment and peace. With age, people often gain a greater perspective on life and become more comfortable with themselves. Mr. Lamb had likely come to terms with his disability over time and learned to focus on what truly mattered. The wisdom that comes with aging allowed him to prioritize happiness and find joy in the present moment.

d) Combination of factors:
It is the combination of these factors – acceptance of his disability, wisdom, and aging – that contributed to Mr. Lamb's happiness. Each of these elements played a role in shaping his mindset and outlook on life. By accepting his disability, cultivating wisdom, and growing older, Mr. Lamb was able to find happiness despite his physical limitations.

In conclusion, Mr. Lamb's happiness was a result of his acceptance of his disability, his wisdom, and his aging process. These factors allowed him to focus on the positive aspects of his life and find joy in the present moment. Despite his disability, Mr. Lamb was able to lead a fulfilling and happy life.