Mike and Al calls out five frequent missteps - chasing performance, holding the wrong risk mix for your time horizon, and letting taxes and fees quietly erode returns. They add that many investors skip a written plan (with cash-flow, withdrawal, and rebalancing rules) and neglect beneficiary/estate housekeeping, which can undo years of good saving. Practical fixes include automating contributions, rebalancing on schedule, coordinating asset location for taxes, and keeping 1–2 years of near-cash reserves. The takeaway: discipline and planning - not hunches - are what keep you on track.