When you're younger and first start dating, you tend to feel the need to have that person be a part of everything you do. You want to hang out all of the time and always be with each other, no matter if you're at school, at home, with friends or going anywhere. While that's totally fine, it's almost like you don't want to do anything without them to the point where you don't know who they are if your relationships end. Sometimes, not all the time, relationships don't need this gap. Sometimes people can actually be together all of the time and they make it work and it works for them, and that's totally great if that's the life they choose. However, sometimes, why those relationships ultimately end, is because one person feels that they aren't themselves or don't know who they are anymore.
As you get older, you begin to realize things that make you happy and make you, you. While you're still dating and trying to find someone that fits into your life, one of the most important things to remember is that it's okay to have your own 'stuff' when you're in a relationship. This doesn't mean material things but something that is yours that you either do by yourself or with others without your partner. It can be a hobby or sometimes that you like to do like spending time alone by yourself - not really doing anything but not having anyone else around either. It's important that your partner also has some things that they do on their own and they respect that you have things that you like to do without them.
When a partner doesn't understand that you want to spend time without them, regardless of whether it's just to go read a book or to go spend time at an art class, it can be really straining on a relationship. If your partner doesn't respect that aspect, it's okay to realize that this might not be the relationship for you. One thing to remember is that if you have something that makes you the best you possible and makes you happy when you do it, don't give that up! A great partner wouldn't want to take away the things that make you happy or that make you feel like you're the best possible version of yourself. Don't let anyone take away those things from you and when you find the right relationship, you'll be able to share why you love these things so much, without necessarily needing to involve them in it. And the best part is, they'll respect that and respect that it's something you love without feeling the need to be involved.
in the end, it's all about being happy. In a relationship, it's okay to have things that are yours and it's okay for your partner to have things that are theirs. it's okay that every aspect of your life not overlap and that you aren't together 24/7. In fact, sometimes having that little bit of space can make your relationship stronger because you both do have those things that make you happy, outside of being happy with one another.