Even though many American couples strive to work together towards common financial goals, personal finance issues can leave many life partners stressed. According to John Hancock Financial Services’ survey titled "How American Couples are Saving Together," one-third of participants felt annoyed or confused about saving with his or her partner. And 30 percent of millennials in a serious relationship already have a financial secret they keep hidden from their significant other.

Outside of saving and retirement planning, 42 percent of Americans involved in committed relationships would put their extra cash of $100 or more towards a shared life goal, while 55 percent would allocate $500 towards one. However, if they received $1,000 or more of extra cash they'd place it in a retirement or savings account.

Respondents considered an emergency fund, vacations and home renovations among key financial goals they’d like to achieve within three to 10 years. However, few respondents considered a wedding as their life goal; only 3 percent would opt to put money towards it. What was even more startling was that saving for a new gadget beat saving for a wedding by 2 percent.

When it comes to how couples save together, the survey found that 74 percent use a joint checking account and 68 percent share a savings account. The top reasons for combining their finances came down to tradition and convenience, while only 7 percent responded that it was to steer clear of arguments regarding finances.

John Hancock Financial Services partnered with Equation Research to survey 1,000 adults (25 and older) in long-term relationships for the survey.

Among American couples that don’t combine finances, more than half responded that they, along with their partner, prefer to manage their finances separately. Other respondents who kept their finances separate said they haven’t had the time to combine them or cited embarrassment, lack of trust, a complicated process and a lack of know-how as reasons.

According to Steve Dorval, the president and head of innovation and advice for John Hancock, the study also confirms the work the company has been doing in the non-investment space. Last November, the company launched a savings and investment app called Twine to address the lack of communication or the lack of know-how, but also encourage couples to not give up on their goals. So far, said Dorval, 10,000 people have signed up for Twine’s services.

Dorval said the app was built for the family member who makes most of the financial decisions.

“We found that generally in a relationship there’s someone who takes the lead,” said Dorval. The leader would then invite his or her partner to join them on the app so they can set and hopefully achieve financial goals together.

Dorval added that Twine is an app that compliments advisor services. According to the report, 52 percent of respondents have never consulted a financial professional about their goals.