Too good to be true

I had a mixed day today, I was going well and on for a good daily total, when 2 out of the last 3 races caught me out, losing over £5 in those 2 races. I knew that one of them was risky, but still had too many trades in place, and they got taken as the market went the wrong way, leaving me with a large red position. I ended up down about £1 for the day, its frustrating to be wiped out by 2 bad races, and I'm not sure how to go about dealing with that problem, it happens all too often and turns profitable days into losses.