If your normal week is at least 3 rides per week, then you should be able to increase the distance you ride. However as suggested, it might be a mental thing that one lap is crossing the finish line.

Might also be that you are just riding too fast for your current fitness on the bike. If you have your HR zones established correctly, then try to stay at zone 3 or lower for at least 70 percent of your ride. That might seem slow at times, but as you get fitter and able to do more distance you'll find that the speed you can stay in zone3 or less will be faster. You have to learn how much energy you can put out per hour to keep you pedaling without wearing yourself out in the distance you wish to ride. And going fast to beat your last effort on that route won't do anything to increase the distance you can ride.

However, don't exclude moments of accelerating as fast as you can or getting to the top of a hill as fast as you can. Just don't work at that effort level for the entire ride.