With the pronunciation of sounds you struggle with, I would suggest making a habit of practicing the sounds every day. That will help you remember what you were taught to do and it will help with muscle memory of where your tongue needs to be, mouth shape, and even how much air to put out. You can just read out loud what you're reading online, or read a book. You don't have to come up with something to say. You could even read the back of a cereal box.
I have never been able to just speak once I started speech therapy. Always one step ahead of what I say I need to think where to do the three things that I mentioned. I find it very tiring, because it takes up so much mental energy to always think about the physical aspect of my speech on top of trying to understand what is said along with contributing to the conversation. However, I'd rather be tired and make sure my speech is clear to those I'm trying to communicate with.
