stick to (one's) knitting
1. To mind one's own business. Oh, stick to your knitting—I don't need to hear your opinion of every little thing I do.
2. To do only what one knows or is familiar with. You can't just stick to your knitting—you have to try new things too.
stick to your knitting
If someone, especially a company or organization, sticks to their knitting, they continue to do something that they are experienced at and do not try to do something different about which they know very little. It failed because we did not understand the plumbing business, and it taught us a lesson about sticking to our knitting! Northern Rock is sticking to its knitting — mortgages and savings.
stick to (one's) knitting
Informal To mind one's own business.