You get 10 gold today. You spend 10 gold an hour later.
You get 3 gold tomorrow, you find something worth 3 gold to buy a few hours later.
Now if you saw this much gold in trade profits, would you go and buy something for 5 gold? The answer should be a resounding NO!
Seriously, you need to stop buying so much from the trading post. Use kharma for your initial level 80 gear. While leveling, mix your unused gear to produce higher quality stuff that you can actually use. I can't tell you how many times I combined a handful of junk blues and came up with an awesome leveling piece of armor or weapon that was just a few levels ahead of where I was playing at the time. It happened all the way up to level 80. If you use mystic forge stones you can get even better gear and weapons with these trade ins.
Also, stop fast traveling so much. If you go somewhere to farm, run around the whole map and don't zip around wasting a few silver each time. Seriously, this is an incredible amount of gold lost if you travel around all day long.
Prioritize what you need versus what you want, and avoid buying gems too frequently. This is a game that is meant to be played over a long period of time, not rushed to max level, max upgrades, and max gem purchases. That's how you end up blowing all your gold and eventually losing real money in the process of upgrading. In fact, you can only make so much gold each day, and it's based on how much you have to begin with.
Force yourself to only spend a percentage of your bank roll in one gaming session. That way if you want to buy something crazy then you need to save up for several days. Use the extremely detailed and easy gold guide to get a few extra gold each day. By limiting your gold output and consistently improving upon your gold input, you'll be saving more than you spend each day. Then you can splurge, as long as you don't spend it all in one go, leaving nothing to invest with!