The Mesilas Yesharim talks about the value of chumros, and imho, the more the better. However, one has to realize that there are three types of chumros:
1. I’m doing a chumra because I want people to think I’m frum.
2. I’m doing a chumra because I’m an am ha’aretz, I don’t know the halachah, therfore I will be machmir so I don’t make a mistake.
3. I know the halachah, I know the different shitos, and while I know we paskin lekula, I want to be machmir because it will have a positive impact on my avodas Hashem.
Number three is (imho) the type of chumra that the Mesilas Yesharim was talking about. Number one should never be done, and number two should only be done when stuck, and you should look up the halachah as soon as you can.
In addition, if we paskin lekula and a person is choosing to be machmir, his chumras should never be imposed on someone else. Better to be meikil then to be machmir and inconvenience others (forcing others to carry because you don’t want to hold by a perfectly good eruv is an example).
Also, chumras are a choice, an instrument to be a better oveid Hashem, and never should be a source of arrogance. As soon as the chumras are causing you to feel arrogant and/or to look down on others, it’s doing more harm than good and should be stopped.