Why do I get such a high and rush when I fix something, I just fixed my cracked screen phone last night?

And it gives me such a good feeling. As being an owner of a house now for a year now I have fixed so man things. Such as my garage door, my sink, my garbage disposal, my laundry. Plus I work in IT and I honestly feel like I feel better than the customer when I fix something of theirs.

Why do I get such a high and rush when I fix something, I just fixed my cracked screen phone last night?
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