Sunny-side

noun
1.
the part upon which sunlight falls:
the sunny side of the house.
2.
a pleasant or hopeful aspect or part:
the sunny side of life.
3.
some age less than one specified:
You’re still on the sunny side of thirty.
noun
1.
the cheerful aspect or point of view: look on the sunny side of things
2.
(informal) on the sunny side of, younger than (a specified age)
1.
The pleasant or cheerful aspect of something, as in Beth always sees the sunny side of events like graduations. This idiom alludes to the area on which sunlight falls. [ First half of 1800s ]
2.
on the sunny side of. At an age less than, younger than, as in He’s still on the sunny side of forty. [ Second half of 1800s ]
3.
sunny-side up. Fried so that the yolk remains intact and uppermost, as in I ordered my eggs sunny-side up and you brought me scrambled eggs. This expression transfers the appearance of the sun to that of an egg yolk. [ c. 1900 ]