"Keep tracking your time & check your actual time against your estimated times. If it's taking longer to accomplish a task, you need to correct that task time, or you'll lose money every time you do that task. It's OK to lose money once, but it needs to be corrected quickly."
That is the secret to sucessful exstimating, over the years watching the pros, they don't use fancy or expensive software, they use their actuals sheets to get accurate estimates.
