Millions of older Americans collect a monthly benefit from Social Security. And for some seniors, those benefits constitute their primary source of income.

In time, you may come to rely heavily on Social Security, too -- and in light of that, you may want to steer clear of these moves.

1. Claiming benefits early

The monthly Social Security benefit you'll be entitled to as a senior will hinge on your personal earnings history. However, your filing age will also determine how much money you get on a monthly basis.

A person with a serious expression at a laptop.

Image source: Getty Images.

If you claim Social Security at full retirement age (FRA), you'll get the precise monthly benefit your earnings history entitles you to. FRA is either 66, 67, or somewhere in between, depending on your year of birth.

That said, you're not required to wait until FRA to file for Social Security. You're allowed to sign up as early as age 62, which could be a full five years before your FRA arrives if you were born in 1960 or later.

But for each month you claim Social Security ahead of FRA, your monthly benefit gets permanently reduced. The earlier you file, the more of a hit your monthly benefit takes.

If you don't have much in the way of retirement savings, an early Social Security claim is a decision you might sorely regret. And even if you do have a decent sum of money socked away in your 401(k) or IRA, you don't know how long your nest egg is going to last. So you might bemoan the loss of a higher guaranteed benefit for life.

2. Filing for benefits late

Just as you're allowed to file for Social Security before FRA, so too can you sign up after the fact. For each year you delay your claim beyond FRA, up until age 70, your benefits get an 8% boost.

Waiting to claim Social Security could make sense if you're low on personal savings and need the higher monthly income to cover your expenses. But do be mindful of the fact that a delayed filing might result in less lifetime Social Security income if you wind up passing away at a fairly young age.

In fact, if your health isn't in the best shape, you might end up regretting a delayed filing. It could mean collecting less money from Social Security than you would've gotten by filing at FRA or earlier.

3. Relying on Social Security for all of your retirement income

Saving for retirement is hard. If you're struggling to do it, you might tell yourself you'll manage to get by on Social Security alone. But that's a decision you might truly kick yourself for as a retiree.

Though your living expenses might shrink once your career wraps up, they may not decline to the extent you'd expect. That's why retirees commonly need about 70% to 80% of their previous income to live comfortably.

Social Security, on the other hand, will only replace about 40% of your pre-retirement wages if you earn an average salary. That also assumes that benefit cuts don't happen, which no one can guarantee. So it's best to set yourself up with additional income from the start, whether it's 401(k) or IRA withdrawals or an investment like a dividend stock portfolio that pays you regularly.

Mismanaging your approach to Social Security could leave you to struggle financially or lose out on income down the line. Be mindful of these moves that might seem reasonable. Unfortunately, any one of them has the potential to backfire on you.