It helps to sell if you like people
We have all met someone that has a force-field of contempt towards all other humans. They could be internal or external to our organisation. Similar to the character, Alice in Dilbert.com. Over my career I have seen many “Alices” across technical, accounting, finance and legal roles.
When you ask for their help, you realise their world view is completely different to yours. You are asking for assistance. They consider you a distraction to their current tasks. They often hate their jobs but take pride in situations where pathetic sales people need their “great” expertise.
Being good at sales means that you enjoy working with other people. Your solutions should help your clients to be more successful.
Even if you do love everyone, there are occasions when colleagues or customers get under your skin.
Using humor can help reduce tension.
In 2009 Arnold Schwarzenegger, while Governor of California was in serious negotiations with law makers to address critical budget issues. Meetings were tense because the outcomes would affect public servants including teachers and nurses. In an attempt to defuse the pressure, Arnold had a bronze caste of bull testicles mounted and presented it to Senate President Pro Tem Darrell Steinberg (D-Sacramento).
The joke did not go so well. See article.
Arnold explained in his interview with Tim Ferriss that we should not take life too seriously. Lighthearted jokes can help us pause and reflect how problems that seem big now will be insignificant in 10 years time.