The universal chirality is the commonly accepted view of nature. Biological chirality is the distinct part of the more general phenomena. Following this view, all living organisms are characterized by the non-equilibrium state of their molecular constituents. From the thermodynamic perspective, the non-equilibrium state of biomolecular ensemble holds inevitable consequences being the substrate of spontaneous reactions directed to equilibrium (not associated with life) state. At the protein level, spontaneous biological reactions represent the natural part of proteins' post-translational modifications (PTMs). The essential contribution to the origin and maintenance of the non-equilibrium state belongs to prevalent bio-molecular chirality. Correspondently, spontaneous PTMs such as racemization and glycation, working against life-supporting prevalent chirality, are known as the significant determinants of protein misfolding, dysfunctions, and aggregation. Accumulation of aberrant protein during life-span allows consideration of time-dependent spontaneous racemization and glycation as protein aging. Spontaneous PTMs of proteins is occurring in the interaction with other forms of enzymatic and non-enzymatic PTMs. In this review, we are considering the contribution of spontaneous racemization and non-enzymatic glycosylation to protein aging.