dj matt good advice. i do that, move the headphones away and/or i turn up the mids high so that the sound is very distinguishable. so that if the drums sound similiar they won't after you do that and you will be able to do the whole track b as an instrument that has to be timed.
also something else that i learned is to stop touching things. you have time once you think it is beatmatched let the track play, in headphones. if you think it is slipping off beat but are not quite sure leave it alone, let it fall off, you will know which one and you will know how bad it is. also if you run out of time. you know if the incoming track is slower/ faster and that you will need to make what adjustments on that track. also it give you time to know how the tracks sound together. also good info to have when making adjustments or making up for a sloppy cue.
also for tighter mixes once i have it beatmatched i let the cued track play. sometimes i am not paying attention to it. but if it falls off after along time i can make slight adjustments.
good luck and remember to have fun.