@tomstafford Just work 40 hours/wk, and don't check business on weekends or vacations.
Become better at estimating by tracking your time vs original estimate (The Personal Software Process book by Watts Humphrey was handier to me than learning COCOMO (Barry Boehm)), or become good at estimating by learn function point analysis, then you can compare your estimates to industry averages. (Applied Software Measurement by Capers Jones has a lot of industry data.)