I always used to convince myself that I was heavily in profit for both poker and sports betting. I kept track of my poker earnings so I knew that side of it was true, but until recently, I had no idea how much I was actually winning/losing at sports betting and just assumed I was up because that's how it felt.
I'm in the UK, and there was some kind of law change recently that shows you how much you have won/lost on a single site. I checked all the ones I use on a regular basis and realized that I am down over £10,000 in the last 5 years.
Needless to say, I now invest most of my money in poker and have significantly reduced my sports betting.