Consent:
The definition of consent is to have permission for something to happen or agreement to do something, but it's so much more than that! Consent is a combination of things like trust & knowledge. One would assume that you wouldn't jump into saying the desired 'yes' without being properly informed as to what you're exactly saying yes too right? You should always ask your questions no matter how uncomfy they might be, it could be a single question that generally ends up making your decision on a situation.
Whether it's borrowing a pencil from your bestie,drinking your dad's last beer, or being tied up and spanked senselessly, it's always important to ask first and receive consent. If consent is not authorized then tuff luck! Respect that person's decision.
'No' is not maybe or a 'Yes' in disguise. Once you decide to not listen and respect the answer given, even if it might not be the one you were hoping for, you are disrespecting your partner/friend/family member. You're crossing their boundaries. Thus forth losing the trust that was once between the both of you.