I am quite happy with this result, because I saw a Chelsea game that could answer the doubts pinned on them. We must know before this match takes place, not many make them as favorites, and even some are very confident saying Arsenal will win. But all that can be answered, especially after they can lead 2 goals in the first half. Entering the second half, Arsenal began to realize that this was not the Chelsea they had seen, and were lucky enough when they could equalize to make the match end with a draw.
You're happy because you're probably a Chelsea fan. 
Arsenal fans feel unhappy, they must expect Arsenal to win the match and get 3 points. It is actually very important, Arsenal needs full points to maintain their position. Now, missing 3 points in the match against Chelsea, Man City overtakes Arsenal position. If Tottenham wins the match against Fullham, they will lead the EPL standings. Man City will be in the 2nd place, meanwhile Arsenal will be in the 3rd place.Regarding the match, Arsenal may be a bit surprised with Chelsea performance. Chelsea could lead with 2 goals, they played more aggressively than their usual game. It's true that Arsenal was a bit lucky that they could equalize with 2 goals in the second half. I think Arsenal a bit late to play offensively, they were not really confident in the first half.
And I think what Chelsea did today they should keep it up, I love the pressure and the defence but as an Arsenal fan I got worried to some extend