To see the letter "F" in your dream symbolizes failure. It may also denote an expletive as in "F you".
The letter F in a dream symbolizes a loss of stability because it's the letter E, without a foundation. F points to a failure to sacrifice or situation that has become negative.
F is also the 6th letter of the alphabet and 6 in numerology represents negativity.
To dream of President John F. Kennedy (JFK) may reflect dangerous idealistic beliefs. Possibly a naive view of achieving power or control never causing others to plot against you. Power or control that is too perfect for others to accept. Experiencing arrogant jealousy or control that erases your achievement as soon as you fulfill your obligations because it cares about nothing except lying to you for good.
John F. Kennedy may reflect a fantastic opportunity to make real change ending up in total disappointment. Total disbelief at how close you got without realizing how enormous the opposition really was that stopped you. Feelings of shock that it never matters how big you get, your enemies or opposition will stop at nothing to prevent you from making a positive change.