First of all, old and young are two words that mean different things to different people.
For example, if you ask a teenager what is old for him, they will tell you 35.
Here are few good examples: Michael Douglas and Catherine Zeta-Jones or Geogre Clooney and Alamuddin with 17 years of gap in between them.
It has to be mentioned that older man and younger woman is a more popular combination than the vice versa.
If you ask your grandparents, they will tell you 40 is young! Age is relative and you shouldn’t put a label on the people you are interested in.
Sure, society has its ways to categorize ages and put rules around who should have a relationship with who, but these rules mean nothing when loves come in.
Knowing yourself is the first step towards self acceptance and self actualization. According to Maslow’s hierarchy of needs, building confidence is a step earlier than self awareness.