Open quantum systems with nearly degenerate energy levels have been shown to exhibit long-lived metastable states during the process of thermalization, as a result of dramatic separation of timescales due to differences between Liouvillian eigenvalues. These metastable states often exhibit nonzero coherences; understanding their physical origin may have implications towards the technologically relevant question of how to maintain coherence in open quantum systems over long time periods. In this talk, I will introduce a Lindblad-form quantum master equation, the "unified" quantum master equation, that captures this effect by preserving the effects of coherences between nearly degenerate states on the evolution of level populations, and vice-versa. By representing the solutions to this master equation in a basis that captures the system-bath interaction more naturally than the energy eigenbasis, I will demonstrate that the separate timescales that emerge in the thermalization can be understood to be associated with distinct processes (e.g., decoherence into a pointer basis, decay of population correlations to the initial state). This approach is paired with a discussion of quantum trajectories, which further provide intuition as to how open system evolution is characterized when coherent oscillations, thermal relaxation, and decoherence all occur simultaneously.