what can i do to prevent myself from getting infatuated with most of the girls who are nice to me??

Choose social activities that help you meeting more people, and purposely ask some girls on dates. If you can't do it because you are not there yet, and you need personal work to get there, concentrate on it. I see from your other posts that you are socially avoidant and dealing with depression, sadly being in that situation and avoiding putting a lot of expectations and wishful thinking on the few people that we meet is really hard, specially because you know you want something you can't realistically have right now. Sometimes you can't help having a crush on someone you can't pursue, in that case try to be less around them until it fades out.

Understand that you're fantastic as is, and EXPECT "niceness" and respect from others, then it won't seem like such an intensity. When you expect such behavior from people, you begin to act in more assertive ways, to demand that behavior, and thusly will have to get to know someone more intimately to start to like them. (:

whenever i get infatuated.. it stays for awhile.. but then it fades away later on.. i wonder if i can ever truly love someone.. let's say i get over this girl i have a crush on in a week or so.. what if i someone else in future decides to give me a boost and i start to have feelings for them again? repeats like a cycle

the only way to stop having a crush on someone is to get to know them better.

Understand the boundaries we all as individuals need and act that way with them.