Garmin - GRMN - Trying to Make New Highs

I still own 30 shares of GRMN and I'm up about 17% - time to sell? I think I want to hold this stock at least through the end of the year, and possibly longer. So if I do end up selling, I will only do it to avoid a short-term decline - and when that decline is over I'll jump back in.

But how would I know a short-term (1 to 10 days) decline is coming? And how would I know when to jump back in? Very good questions - I would try to anticipate the price movement by examining the chart and the technical indicators.

Take a look at the chart:

I'm going to wait and see if GRMN can power through resistance at $105 - today it tried to break through this level for the third time , unsuccessfully. GRMN has formed what is known as an Ascending Triangle - a bullish chart pattern. The moving averages and the trendline are rising up underneath - they may help GRMN break through. I don't like the looks of the MACD lines or the OBV line, however. They are weakening as GRMN is treading water. If GRMN breaks through into record territory, I may consider buying more. If it closes below its trendline, I may consider selling.