It seems like you are having problems with adjusting with the office environment and that is making you anxious and tense. You see it will be impossible for you to make the environment conducive to your liking and change behavior of people who act not according to your taste and disposition. So, what you can actually do is find like minded people at work who are non-judgmental and accommodating so that your spirits remain high and anxiety low at all times in office so that your work is not at all affected and you have a bunch of people to share your sentiments when you are feeling emotionally overwhelmed.
Having said that the bot***** *****ne is that you will have to try hard to modify your personality which is slightly more sensitive and try to develop a thick skin so that you are much more emotionally resilient and strong in warding off such work related disruptions.
As far as the problem with one particular team mate is concerned, i am sure you have made it clear to him that you do not see him through a romantic lens and you would only want to be friends with him, but if this is too bitter a pill for him to digest than it is his problem how he deals with it, as time passes by may be his maturity will take over his passion and sense will prevail and he will come around as a friend, so give him some time to come to terms with it and remain cordial with him.
If for some reason despite trying all of this you still feel anxious at work then you may seek therapy called as CBT from a clinical psychologist and learn coping skills and strategies at fight off stressful situations at work and daily life situations.
Having said that i feel you have it in you to make some modifications in your own personality like becoming a bit more resilient and cordial with colleagues and practical and not taking things said and done in office t your heart and maintaining a safe distance with one and all so that you do not get riled up emotionally. Slowly, you shall be able to adjust well within the realms of your workfront and will be able to manage tricky and stressful situations at work place better.
I hope this makes sense. Just remind yourself that you will not back down with any sort of challenge thrown at you and try to distract yourself when stressed out by concentrating on things which bring joy to you, you will be all fine eventually.The situation at work may not be to your liking and they cannot be changed but you can change your persona slightly so that these things do affect you any more.
Wish you all the best.
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