...suprised more often if the mainline move is not played since I probably subconciously expect mainline moves.
You don't mention openings anywhere else in the title or OP, you don't post the thread in the opening section, then you randomly throw this in? If you're in the opening and you know the mainline then how is that making a conscious effort to predcit anything?
In order to make your own moves/plans you have to always anticipate what your opponent will do. Of course I can't anticipate all their moves/plans, so suprises happen regularly. When they do, then hopefully my pieces are placed in positions that allow me to discover new moves and plans:)
If there are no forcing moves, it's not possible to make reliable calculation. You think more in schemes or patterns.
So not calculating early in the opening is just part of being an experienced player... as long as there are no forcing moves. Some openings get wild quickly of course, so then you will definitely be required to calculate.
Is this a good habit to develop or keep? I'm talking about after every move you would calculate into all your opponents decent or good moves several moves deep as way to practically never be suprised. By every move I even mean opening moves. I used to do this a lot when I first started chess (probably out of caution) but as time went on I started to not really do it as much for some reason. Thats not to say I completely ignore my opponent but I don't bother "predict" all his possible sequence of moves and come up with all the possible solutions/replies I can play against them with the exception of critical moments. As a result of this natural change of not "predicting" as tediously the only obvious change is being suprised more often if the mainline move is not played since I probably subconciously expect mainline moves. Honestly I don't think any chess player likes to be suprised.