Dreaming - you are so young! Far too young to be worrying about this, if you don't mind me saying.
I didn't meet DH until I was 30. Even then, the early years of our relationship were tough - he is older than me, and had come out of an extremely dysfunctional relationship, and had all kinds of baggage associated with that. He actually asked me to marry him, and then had a total panic about the commitment - we had to cancel the wedding. I stayed with him because I thought he was wonderful, and because I could see clearly that he was suffering from a bout of anxiety so serious that it definitely qualified as a mental illness. He went to counselling and sorted himself out - he became not a different person, but a different and more confident version of himself. Last year we even managed to get all the way through a wedding without incident
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Despite this rocky and unpropitious start, we are really happy, in the sense that I honestly believe there is nothing either of us would rather do than spend time with the other. He tells me he loves me five or six times a day, we're physically and emotionally close, and we write together, which is an intimacy that I think probably involves quite a bit more trust and synchronicity than sex in some ways.
The day before I got married, a lady in a shop who had been married for 50 years told me 'It's great, but you have to work at it'. She was right- a relationship is like a creation that you continue to build every single day, and it's the little gestures, not the big things that really matter. Refusing to allow hostility, anger, resentment or contempt to creep into any corner of everyday life is important. I also think that healthy trust is something you live, not something like faith that you place in an abstract - it's about having the humility to realise that you are not perfect, and that temptation is not something to be trifled with. Our email accounts, phones, letters are all completely open to each other - and this doesn't feel like a constraint, it's just normal. If I were ever to feel that I couldn't show DH something, if I needed to go behind his back, that would be a massive red flag. We also socialize a lot together, rather than going out a great deal with separate groups of friends in single-sex groups, and we don't bitch about each other in private to friends.