The problem with the tense is that it does not match the sense of time indicated by the word since. Since means "from a starting point until now." Therefore, the time in your sentence spans from when you were 12 years old until today. The present perfect also indicates a span of time from the past until today, which is why it often is paired with since.
Notice the difference in time between these two sentences:
Since I was 12, I have played basketball almost every day. (The span of time is from the past until now, so we use the tense that also spans the past until now.)
From the time I was 12 until I graduated high school, I played basketball almost every day. (The span of time is from one point in the past until another point in the past, so we use the tense that is entirely in the past.)
Just be aware that since does not always indicate time. It can also mean because. When it means because, it does not necessarily pair with the present perfect.