A common example is contributing too much to a Roth IRA based on your income level; the ability to contribute to a Roth IRA begins to phase out at higher income levels. Contribution limits decrease once your Modified Adjusted Gross Income (MAGI) rises above $105,000 for single filers and $167,000 for joint tax filers.
(A high rate of return, of course, will beat that, but you'll have to work for it.) Assume that inflation is an annual 3% and capital gains are 15%. If your target is a 15% return before inflation and taxes, you'll end up with 12.4% return. (If you pay 20% in capital gains taxes, you'll end up with 11.6% return.) A really good return on investment for an active investor is 15% annually. That's healthy.
The internal rate of return on an investment or project is the annualized effective compounded return rate or rate of return that sets the net present value of all cash flows (both positive and negative) from the investment equal to zero.