“Spirit” is one of those problem words that have several meanings.
My Christian upbringing taught about the Holy Spirit as the third party of the trinity, also referred to as the “Holy Ghost”. At Pentecost, it possessed the disciples and enabled them to speak in tongues that each listener heard in their own language. And it comes as a “comforter” that helps the Christian mature in faith. As a Christian matures, their nature slowly changes through a process called “sanctification”. Temptations that once plagued the immature Christian no longer carry strength or influence.
As one who is trying not to believe in ghosts, I use the term “spirit” a little differently. We sometimes hear of someone being “mean spirited” or that people worked together in a “spirit of cooperation”.
Our spirit is how we think/feel about something. It’s not just a feeling, like a cold wind on your face. It’s not just an emotionally neutral thought, like “2+2=4”. But it is our anger when we see someone mistreated. It is our joy when we see love and caring in action. And it is the peace we feel when we lay our worries aside.
Our spirit is the attitude we employ when we do the right thing. We can either experience it as an onerous duty or we can experience it as a joy of service.
One key function of religion is to help train our feelings, so that we feel good about doing good and being good. To me, that is the definition of a “holy spirit”.