It sounds to me like you feel like you are being taken advantage of by someone who you care for. Maybe you're not sure the person really cares for you the same (hence the aliens) They are pushing you away or not being the way you would want them to based on what you are giving them. This is obviously causing you great distress.
The truck...maybe you feel like you can't tell this person how you feel about them taking advantage of you so you need an outside source to push them away which like you said would be better for you since you wouldn't feel so 'alienated' but you are afraid to do this because you don't want to hurt the other person nor suffer the consequences yourself (guilt, loneliness, etc) of letting that person go. A lot of us are scared of change and that is what breaking away from the building is-change. You are not sure what is going to happen so you are scared.
Are you in a dissatisfying relationship with someone or something (I just realized this may not be someone at all but something)?
This is just my opinion. I would be interested to know if anything I've said applies to a situation you are dealing with.