I get the same feeling each time so what I tend to do is start out buying a tiny bit so at least I'm invested. If it goes up there is profit and if it goes down you have the option to buy more while having incentives with the already made investment to somewhat keep track of what is going on. Once you get into it it can be quite addictive though. The reality though is that a very low % of holders in the end will actually make profit so if you can get out on average 50% below the eventual top I would say it's a great success.

Good Luck!