This paper deals with almost sure convergence for partial sums of Banach space valued random variables. The results are then applied to solve similar problems for weighted partial sums of conditional expectations. They are further used to treat partial sums of powers of a reversible Markov chain operator. The method of proof is based on martingale approximation. The conditions are expressed in terms of moments of individual summands. (c) 2023 Elsevier B.V. All rights reserved.