Novak Djokovic’s disqualification incident reminds me of one of Nadal’s interviews where he talks about how he’s able to check his frustration on court.
Anytime a player is frustrated is because s/he believe they are better than the result of the last point/game/match/career.
However, the performance(result) on that point/game/match/career is an EXACT reflection of the effort/focus/skill/ability that was put in.
Keeping this in mind will keep your ego in check the next time you’re feeling frustrated with some result.