Experienced a go around for the first time. What are the possible causes?

[pax britanica]

I have had rather a lot of GA statistically speaking , most were due to traffic failing to clear or not gettign airborne quickly enough.

I am always impressed how aircraft like a 747 which climbed pretty slowly on a normal take off but on a go arounds x thousand pounds of fuel later it climbed completly effortlessly.

Oddest, animals on Runway in Rangoon many years ago