I recognize what you're saying, there are times when the Spirit just seems to infuse what you're doing with more than usual power and the results show. That said, the term 'anointing' is really meant to simply mean 'the power of the Spirit to accomplish a specific purpose'. So when Jesus stood up to proclaim His mission statement, He started off saying 'The Spirit of the Lord has anointed me to . . .' I find that I have an anointing to teach. It doesn't matter whether or not I feel anything special happening. If I prepare properly, both materially as well as spiritually, the Lord works through me whether or not anything seemingly special happens. The most frequent comment I receive is that people say they understand Scripture and the Lord very clearly. Sometimes, the Lord seems to infuse a little extra humpf into the mix while I'm teaching, as when someone gets Baptized in the Spirit just listening to my teaching on it - something that's happened a dozen times or so over the years. But even when that's not happening, I trust that His anointing is at work empowering the message with His purpose to the audience.
I would also clarify that I was not always anointed to teach. At one point, I accepted an offer to teach a class in Church. It was a train wreck. I failed miserably and checked that off as something never to try again. Then one day I was in worship and the power of the Spirit came on me. I had to just sit down and rest in Him for the next half hour with my eyes closed and tears streaming down my face. In that time, I heard the Lord tell me He wanted me to teach. I argued back that I'd tried it, but failed. He just repeated it over and over. So I started a Bible study in my house . . . it was immediately obvious something had changed. I still needed to prepare and learn how to teach, but there was an anointing for it now that was not there earlier. So I would disagree that we are new born with it. I believe the Spirit gives it according to His timing and will. Even Jesus didn't officially receive His anointing until the Spirit descended on Him when He was baptized, which He then went out into the desert to be tested and then came back and launched His ministry with that announcement from Isaiah I referenced already.