Dear Wang Lin,
I guess could understand your trouble now!Nobody would like a guy who keeps saying your drawbacks day and night.However,it's also important for you to know how to get together with colleagues,even a guy like this!
Criticals from other people can be either reasonable or nonsense.When facing a reasonable suggestion against your poor side,accept it with smile and gratefulness.It's rare that one man beyond your parents would tell you your weakness and wish you get improved.Remind yourself to follow the suggestion and say 'thanks' to the guy!
If the saying doesn't make any sense to your situation,do not deny it directly or start a fight!No matter he is envy or for your good wrongly,keeping yourself calm is always the best solution.Thus you won's hurt sombody with good intention and you won't hurt yourself by an angry arguement!
Unfortunately,however,it's really hard to judge whether one suggestion is right or wrong since different people have different standings and understandings of each other.In this case,communication is the key!Try to let your colleague know your condition and explain why you couldn't accept the suggestion or change yourself!And try to understand the intention of your colleague and why he could see your weakness.Try to be frank during the conversation!I guess that it not only solves your problem but may also bring you a good friend!
Best wishes
Li Hua