Ahh the trap of the young; that is, thinking that sayings are universal and apply to all parties in all situations at all times. As you get older, you begin to recognize nuances in sayings and words, and employ those distinctions which best serve you.
Your word is your bond is an excellent way to conduct yourself in business as it serves you, your reputation, and your clients. It permits clients to trust you and send you referrals. In business only, I conduct myself in such a manner.
However, with women, in some cases, it can and will work against you as it makes you predictable. To be predictable, to give her certainty is anti-attraction, which serves neither you nor her.
Commit to those actions which best serve you and the other party--shamelessly and unapologetically too.