"If you feel lonely when you are alone, then you are in bad company".
I pretty much live by that. Been a happy loner and introvert for most of my life, which served me well when I moved from Argentina to the US at age 23 and pretty much didn't know anybody here. I lived in a 200 sq./feet "efficiency" for about 4 years, saving 80% of my income and reading, listening to music and watching at least one movie per day, thanks to Netflix (those three activities basically define who I am since I was at least 10 years old). When most people my age where getting up to their eyeballs in debt, getting drunk, getting lost in life, getting high, or a combination of all of the above, I don't regret having gone through this "sacrifice stage" at all, and I am grateful I saved as much and lived below my means for so long when it would have been a lot easier to just go with the flow of the masses...
I am now 32, recently married, and life is very different. I still value my "alone time" as perhaps one of the most treasured aspects of my day, and my wife knows about this. She's not quite as independent, self-confident nor self-reliant as I am, but knows how important (and, in the end, beneficial to her) it is to "let me be" as much as she can.
The way I handled this was easy: before we moved in together, I told her she could do anything whatsoever she wanted to do with the house when it came to decorations, arrangements, furniture, etc, as long as I could have one room fully for myself (our house is a 2/2, which is more than big enough for me) and do with it whatever I pleased. She agreed, and now whenever I feel like being my usual self I simply say "I'm going to the room for a while". This operates as both my "sancto santorum", my "man cave", my reading place, my music listening place, my relaxing area, and my "home theater" (all my audio-visual equipment is set-up there). We do, however, make a point of watching at least one movie together every night, and we both love that. I think the fact that we both love movies so much, even though it might sound so irrelevant and simple, is in fact a crucial aspect of why our marriage works (so far).