Never buy in hype when the price is high, that seems to be your major problem. Also never sell when you are loosing, just wait and it will eventually go up. With selling you are throwing that opportunity of getting your money back straight out the window.

Get some coins that you like for the technological solutions they have to offer. To me EOS and NEO are best long term holders currently.

EOS is the future of blockchain and NEO has great potential and allows you to earn interest on PoS