HI,
I can completely relate to this , before I used to have a similar problem. I analyzed it deeply , started working on my endgames and this is the most crucial part I tried to develop patience towards the end game you just wanna go home and seeing that you have an advantage you try too hard to convert . Yeah there is one more thing called chess stamina the longer the games go the more exhausted you get.
If you need any help feel free to reach out . I hope this helps 
Hi,
since I started playing classical OTB last year (FIDE classical should clock in at around 1500), I noticed a frustrating weakness in my play. I regularly get into positions, where in the late mid game/early endgame, I get positions being around +1/+1.5, being a pawn up or having a passer, but I really struggle in converting these positions. In other words: positions with an advanced pawn with still a lot of pieces on board, but I have problems using this pawn advantage to convert to a winning position.
I know basic rules like getting your rooks behind your pawns, exchange some pieces but not all of them (very vague), maybe exchange 1 pair of rooks etc., but I have trouble finding concrete solutions and more often than not I will lose my advantage/advanced pawn.
Maybe someone has some sources they feel like they helped them with this topic? Books, online classes etc., I would like something concrete but maybe it is just a more general topic of getting from an advantageous middle game to a winning end game. I am just curious what your thoughts are and what you would say helps in improving concerning this issue
Thanks a lot!