This phenomenon seems to affect everyone from time to time. You never seem to be trading better but your equity just hovers around the same level, winning some and losing some. It can get very frustrating to the point of giving up forex trading. We understand that since we went through that as well.
Or let's say someone actually wins some money in a casino, instead of leaving the casino with their winnings, they make bigger bets since they feel that they are on a winning streak. Often, when you lose something that do not belong to you in the first place, you do not feel that much pain. However, when you start losing your life saving, you start to feel the hurt.
Back to forex trading, you should treat forex as your own business and treat each trade as a new business which you are investing in rather than treating it like a gamble.