Sometimes it gets too much

Hey ladies,
Whenever I get turned on it feels really good and builds up until I feel like I'm nearly there and then sometimes out of no where it will feel too much and like I need to stop and take a break and all the good feelings just disappear. 
I don't know if I'm doing it wrong, sometimes it goes great and I don't have any problems and sometimes it just gets too much. 
Has anyone experienced this? Do I need to keep pushing through that feeling or do I just take a break for a while? Any ideas?