What do you say?

What phrase do you say to your toddler when they want to do everything themselves and have meltdowns when they don’t ? For example, sometimes I shut the door before he does and he will have a meltdown saying “baby do it”. I usually try to let him do most things, but occasionally I have to do something. I’m trying to acknowledge his feelings, telling him next time he can because I also don’t want him to think by screaming I will give in. Advice?