You have only been running for a year, the first year everything is a exciting and you are constantly crushing PB's.
For example on a 5km. You go from like 45m-40m-30m pretty quickly then you drop to 29.30-29-28.30 which slows down then it takes a huge effort to go from 25m-24.30 and you are fighting for seconds. You will eventually plateau but occasionally get a 21.55 instead of a 22.30 for example and you have to be happy with that.
Unless you train like an Olympian you ain't going to get Olympian times and for me I came to terms with that. I enjoy running and enjoy putting in x amount of training when I put in religious training with extreme times I'm always tired, injured, lose my passion for running and don't have time for my family.
So it comes down to a performance vs happiness scale. I have run 19m 5km but the amount of training to get me there makes me an unhappy person so I feel balanced at a 25min 5km and my/family happiness is at its peak.
The other thing is every year I get older and it takes way more effort for me to push myself to great times.