Ways to combat negative self thoughts

For as long as I can remember I’ve always been a half glass empty person. When I say for as long as I remember I mean like 5-6 years old. I have always had a negative look on life. Whether that be the nature/nurture of growing up with absent parents or purely out of self. I’m not sure. But what I am sure of is I’m tired of it. I hate thinking so negatively all the time. But it seems like when I’m trying to be happy and optimistic I can hear the self doubt screaming louder and louder. I have little to no empathy for myself at all and always feel like I’m never doing enough. Are there any proactive things I can do in my day to help think more positively about life and myself? Because I truly want to stop feeling this way, I just don’t know how.