Over at YC:HN, I gave some advice to an entrepenur who was feeling the opportunity cost of not taking a job offer from Facebook:

"I can't rationalize that being worth a few million bucks though."

DANNY: The skills and experiences are worth more than a few million dollars.

"I love what I do, and I've built something users love."

DANNY: You have a success story, don't sit on it and just wish for the best things to happen to you. Keep shipping. Keep building side projects. Keep learning new things.

Following the IPO there will be many people who have cashed out and will look at the general investment market (equities/bonds/fx) and decide that they'd rather roll the dice and invest in what they know: startups. Keep networking, keep up past relationships, and don't burn bridges unnecessarily. When you're ready to raise funds for a project that needs outside capital, you want to have a black book full of names and numbers of people that have the wealth and connections to get you funded.

There will always be opportunity costs to every decision you make, stop thinking about the "what-ifs" of the past and start thinking about the "what-ifs" of the future, based on what you do today. Then get to work building that future.