To disable this feature, take a craft knife and cut the little track between the two solder pads. If you do , you'll need to press reset manually when you upload a sketch. The solder pads are there so you can re-enable it if you get fed up of losing the auto reset. 
If you can disable DTR in your serial terminal, it saves you having to butcher your arduino.
You could at a push solder some tiny wires to a toggle switch or something to be able to switch it on and off, but it would be easier to buy a seeeduino.