If you are mentally drained from someone maybe you should examine yourself first before placing judgement on the other person.
Time heals all. Get yourself some happy-making adrenaline rush too. if you cant go bungee jumping. get all chilled and relaxed in a hot shower then suddenly blast it icy-cold until you're practically hyperventilating. its a quick mood lifter.
Remembering how happy you used to be and knowing that its possible to be in that place again!
Also the question 'will it matter in 10 years' is a good one.
Go spend some time with really good, positive, calm friends. Get shit off your chest if needs be or just do something that you enjoy. Traveling could be good as it will remove you from your immediate situation. Try to keep yourself occupied so that you don't get stuck in a rut.
It's all about how your day starts , if u can wake up and have a positive thought then positivity can come through out your day.
Write, draw, compose, play with instruments and try to get as creative as possible. Remember to be as strength as you can be and man, life is like a wave. Goes up and down, if you need to cry, cry. Speak with your friends but don't seek her back! Page passed shouldn't be looked back. I once wrote a song that says: "there's something amazing that we're starting to realize, the broken mixed parts of our life together like a phoenix, are stronger and full of life" it's all an apology to failure! Don't worry, happens to all of us, learn as much as you can from your pain as well.
Self destructive people are contagious because we allow them to take so much from us. I had an ex who was the same way. She was selfish, negative, critical, judgmental, and extremely demanding. Everything was about her and nothing was ever good enough. I love to help others and I thought that I could be the one to save her from this self imposed victim status. But, along the way I let her impose her identity on me. I was unhappy and my life suffered. I finally ended it and cut her completely out of my life. I took time to nurture who I was by finding the love in life again. I focused on spending time with family. I started doing the activities I loved doing again and took time to explore new things that interested me. I believe that sometimes feeding yourself is the best medicine.
Don't drink too much alcohol or consume any depressants to numb your emotions (if you're that way inclined), even if you feel shit and frustrated and want relief. Your brain needs to go through the process it's going through with how you feel. If you try and escape it it'll catch up with eventually and you'll be fucked up in the meantime. Based on my experience anyway. Otherwise, try and allow yourself to feel angry, upset, whatever emotions you have and work through them, even if you feel like shit. Sometimes it's the only way but know that everything will pass and you'll learn from it and it'll get better. Sorry not very chirpy but sometimes things are hard and you need to go through the process, there isn't really much you can do. Exercise helps but it's difficult to motivate yourself to do that. I'd walk a lot. Try and read/watch things I'm passionate about, remember who I am individually and what I want from my life and future, etc.
Other people don't fuck you up, you fuck yourself up over other people. Get your power back.
I'd stick to the love yourself tho.. Loving yourself, and being less focussed on others doesn't mean you can't help others. Loving yourself makes a person emit an incredible energy: (self)confidence. And with that, you'll help and attract people whether you want it or not.
If you believe in yourself, others will too, and come seek your help if needed. Don't be afraid of being selfish or carefree either.. or actually.. dont be afraid of people thinking you are so
You know who you are, you just have to stop looking for it, and just be.
I should add that being yourself means if your sad, down or depressed.. then you ARE sad, down or depressed. When I get depressed, i try to actually express this as much as possible, keeping away from the smiling mask I'm used to. This makes me more aware of how I'm feeling at that moment. Embrace the down times just like you treasure the good times. You just went through a hard time, you deserve to take some time off, lay back for a while and just be good for yourself.. you could even spoil yourself a little. "Don't cry because it's over. Smile because it happened" Dr. Suess.
You can write out all your thoughts. Write out everything. Write out the mistakes you think each person made. What did you learn from it? Make peace with the whole experience. By getting it off your chest and writing out everything, you can approach the situation with more well thought out approach.