All of the above advice is more co-misery than actual help if the end result you desire is a method that will provide you with art that you feel reflects your personality at its most brilliant. There is a better way.
But first allow me to be of emotional assistance. OP you are only 18. Which has 1 main advantage and 1 main disadvantage. The con is that you likely have very little experience. Which accounts for your lack of confidence in your tunes. But dont feel bad cause you have time on your side. There are MANY illusions in the creative process that you can see through as you progress. Your goal should be to gain as much XP as you can while you can, so that you dont waste the opportunity that comes naturally with the brevity of youth.
NOW, heres how to write great lyrics every time, easily. MAKE A SEED LIST.
Seed list is a list of words that have high emotional impact, that you personally like the sound of. The word PHANTOM for example. Its a great high emotionally impacting word that also sounds cool when spoken. So go through ALL your favorite albums and books and movies and write down in categories of nouns, verbs, adjectives, etc EVERY ONE YOUD LOVE TO USE. That is the part of the process that makes it YOUR personality. You will need hundreds of each category. ONLY CHOOSE THE HIGHEST EPA WORDS. That way youll be using only or mostly words that due to connotive value in society will leap off the page. Then start narrowing the lists down over time. Circle the words and phrases you MUST use that you personally LOVE.
Then start rhyming them in couplets based on standard rhyme schemes and study up on the emotional impact of the different types of rhyme (true, near, mosaic, wrenched, etc)
In time you will do this procedurally, no longer sitting waiting for an idea to happen to you, you will make it happen.
This sht works man, youre welcome