I'm currently experiencing the same thing. Where I'd be doing great, building up my br slowly. ( I deposited $200 and i'm playing $10nl, gonna move up when I have 25 buyins ) then I'd get hit either by a bad beat, or things like flopping an under set, having an overpair against a set, etc.
Im trying to just play through it but it is starting to get on my nerves. It's not the money, but I just feel like i'm not really getting anywhere, and my br is never going to build up high enough to jump to the next level.
Is there any advice on what I should do? Should I multitable more? Right now i'm playing 2 tables.