Arising from a deep thought and personal experience, and with a sense of humor, I hereby affirm as follows:

The level of success in life is a multi-variable function of "hard work" and "God's grace/favour" with time as a parameter.

Inherent in my affirmation, which may be taken as a UNIVERSAL LAW OF SUCCESS, are several axioms.

FIRST AXIOM: Time is the only universal parameter. All things being equal, The earlier one gets it right by way of hardwork and not going against the grain, the higher the level of success that will be achieved.
Example: Someone with a sharp second-class upper at age 20 will very likely achieve higher level of success than someone with a first class at age 40 provided other conditions are the same for both.
NB: The time scale/interval with respect to the FIRST AXIOM varies from location to location.

SECOND AXIOM: Other parameters in the two-variable model are functions of the boundary conditions (laws and policies, level of corruption, value system, adherence to merits, quality of education, nepotism, tribalism, ethnicity, etc) of the location where the person is located.
Example: Though the general form of the model equation will be the same for Nigeria & USA, the model parameters and time scale will differ. Thus, a 25-year old first class in the USA will achieve higher success than same in Nigeria.

THIRD AXIOM: The two variables ("hard work" and "God's grace/favour" are linearly combined by fractional weighting parameters whose values are location dependent. However, there is a universal minimum for the weighting parameter of "God's grace/favour" variable and as such, a zero value is ruled out. For example, the weighting parameter for the "God's grace/favour" variable will be far lower in USA than in Nigeria.
NB: Everyone has a minimum degree of success because the gift of life, which is from Almighty God, is an integral part of success.