How can I be less impatient?

For years it has been so that I'm extremely impatient and prefer to have what I will get in days or weeks. If I look at a car and buy it and the seller can only give me that in a few days, I leave and don't want the car anymore, I then look at one on the same day that I can take away with me. And now it's a new cell phone. I should be able to get it today but the seller apologized and asked me to get it on Saturday. The problem is now I'm looking for something that I can get right away. Unfortunately I can't find this model, which is why I'm a little angry. And that's exactly the problem if I don't get it right away on the day I want it, I get angry and sometimes aggressive. This is also how it is when I order something and it arrives 1 day later, I always look for reasons why I need it on that day, just to maybe get it earlier. In addition, I actually wanted to buy a new car, which costs a little more, but it takes me too long and I bought a new PC and a Nintendo Switch with the money just because I expected that I would get the money up to get together at the time. So how do I stop being so impatient?

It's best not always to give in to your will and sometimes wait a day for something. There's no other way to learn

One can only advise that you deliberately withhold things from yourself for a few months. Start small. Go shopping, decide on something that you don't urgently need (luxury foods, etc.) and postpone their purchase to the next day. Then three days later. If that works out well, by a week. Do the same with online purchases. Fill the shopping cart and then set in the calendar when you "may" buy.

Keep practicing this until you can wait without any problems.

In the days when you have to wait, consciously find activities / projects that will distract you from waiting. You can also say, "only when I have cleared my basement will I treat myself to…". That motivates a lot to muck out the basement.

Start with small steps by, for example, postponing purchases of things that are not important for a short period of time. It also helps if you are aware of what you can, want and have to do during the time you have to wait for your cell phone, for example. Make a list of tasks you need to do and things you want to do and start working through them. That is a good distraction. If you still get angry or aggressive, counting helps. Really. Just count. Count until you are neutral again and then do something else.