user21427: I've been practicing mantra for quite a while now & received empowerments for a few. The main ones that I practice are Guru Rinpoche, White Tara, Vajrasattva 100-syllable. I take care not to go for those which require extensive samaya so that I don't break vows.
I rotate between several mantras, sometimes depending on my mood, sometimes to address a certain life situation. For example, practicing White Tara or Medicine Buddha when I am physically ill.
Generally I feel like they are all effective(?) and I don't know whether I should just pick one to focus on, or just do what I'm doing now and spread my effort out over a few practices. I understand that on an ultimate level, it doesn't really matter because all Buddhas have the same realization, but on a mundane level, how do you know which mantra suits you?

user12953: Look at what happens to your mind through chanting them.
I find 'Om mani padme hum' powerful because of the deep yet concise rememberance, discussed here: What is the meaning of 'Om mani padme hung'?
But I found a Hindu mantra in English that I really connect with 'I am not this body, I am not this mind: I am, I am, I am'.
It is more important to really chant, with commitment, to follow the experience, than to pick and choose words though.
Here is a teaching letter from Seung Sahn on mantra practice.

21427: <p>I've been practicing mantra for quite a while now &amp; received empowerments for a few. The main ones that I practice are Guru Rinpoche, White Tara, Vajrasattva 100-syllable. I take care not to go for those which require extensive samaya so that I don't break vows.</p>
<p>I rotate between several mantras, sometimes depending on my mood, sometimes to address a certain life situation. For example, practicing White Tara or Medicine Buddha when I am physically ill.</p>
<p>Generally I feel like they are all effective(?) and I don't know whether I should just pick one to focus on, or just do what I'm doing now and spread my effort out over a few practices. I understand that on an ultimate level, it doesn't really matter because all Buddhas have the same realization, but on a mundane level, how do you know which mantra suits you?</p>
 12953: <p>Look at what happens to your mind through chanting them.</p>
<p>I find 'Om mani padme hum' powerful because of the deep yet concise rememberance, discussed here: <a href="https://buddhism.stackexchange.com/questions/7477/what-is-the-meaning-of-om-mani-padme-hung/45854#45854">What is the meaning of &#39;Om mani padme hung&#39;?</a></p>
<p>But I found a Hindu mantra in English that I really connect with 'I am not this body, I am not this mind: I am, I am, I am'.</p>
<p>It is more important to really chant, with commitment, to follow the experience, than to pick and choose words though.</p>
<p>Here is a teaching letter from Seung Sahn <a href="https://kwanumzen.org/teaching-library/1977/09/14/low-class-practice" rel="nofollow noreferrer">on mantra practice</a>.</p>
