Meditation, that is just relaxing, closing your eyes, and letting your mind wind down a bit is perfectly fine. Meditation as a means of helping deal with anxiety can be really beneficial.
Likewise meditation upon the things of God, that is contemplation upon Scripture and upon God's faithfulness or upon the work of Christ etc is also a good thing.
The only issue would be participating in spiritual and religious practices which are foreign to Christianity and which encourage non-Christian spirituality. Not because there's some sort of sinister force at work there, but simply because it provides no benefit to us and encouraging false beliefs in ourselves can itself be a problem.
That's why yoga, as a purely physical exercise involving stretching and breathing is completely fine. Yoga as a specifically religious practice as practiced among the Dharmic religions would not be fine.
So you mention chakras, but there's no such thing as chakras as far as Christianity is concerned; this is a concept found exclusively among some Dharmic and other Eastern religious philosophies. So I'd recommend just ignoring the whole notion of chakras altogether. But there's nothing wrong with closing your eyes, breathing slowly or intentionally to help calm your nerves or focus your mind.
In fact, why not use that time of meditative relaxation to also set your mind to good spiritual matters, like use it as another opportunity for prayer.
Find some quiet time, use a daily devotion, something perhaps like the Daily Office with prayers and Scripture readings that you can focus your mind on and just enjoy a time of private prayer.
As far as the voice you say you heard, there's probably no reason to believe it was anything other than just your own thoughts.
So the TL;DR version: Don't worry, you can meditate or just close your eyes and relax without any worries. When you meditate, use Christian meditative and prayer sources rather than look to other religions; as setting your mind upon the things of God will actually be of benefit to you spiritually.
-CryptoLutheran
